user: I was wanting to look into possibly upgrading my seat (GINX36) but the seating chart says 1st class and delta comfort are all gone. That's impossible.
agent: Hi Freddie, thanks for contacting us. My apologies for the inconvenience. One moment while I look into this further. *HML Thanks for your patience. I'm showing First Class is sold out for your flights; however, Delta Comfort + is available. The Delta Comfort + cabin is sold as a fare for this market; therefore, in order to confirm Comfort + there will be a difference in the fare. *HML
user: What does this upgrade list mean? And this one for the first leg of the flight?
agent: It looks like there may an error between our system and the app. I'm checking into this now. *HML
user: ive heard about airlines blocking out seats for the purpose of overbooking and juggling to squeeze profits. I didnt know you guys were still doing that or doing it period
agent: Thanks for your patience. I am showing seats available in First Class; however, the lower First Class fares are not available. Once your reservation is changed to the First Class cabin, you will be able to view and assign seats. *HML You may see more availability closer to the time of travel. *HML
user: This explanation sounds very convoluted. 1st there was no seats available, now there are seats, but there are no more lower 1st class fares available? What's does that mean and how do I upgrade seats. That's the whole reason I tweeted you. Cmon Delta aka *HML
agent: Freddie, in order upgrade your ticket to First Class, you must pay the difference in the fare. In reviewing your ticket, you have no value left to apply towards the cost of the ticket to upgrade. *HML If you're using miles to upgrade, the cost is 35,000 miles each way and you must be booked in a L, U, or T class fare. *HML
user: What do mean I must pay the difference but then say I have no value left in my ticket? Why not just tell me how much it is to upgrade like I've been asking from the beginning? What does it mean I have no value in a tix I purchased?
agent: To make changes to your reservation there is a change fee of $200.00. Your ticket is less than the change fee; therefore, there is no value in your ticket. I can provide an estimated cost to change your ticket; however, this does not include taxes and fees. *HML The estimated cost is $1,500.00 for First Class on your flight from EWR to GCM. This does not include taxes and airport fees and fares are not guaranteed until purchased. Please contact our International Reservation specialist at 1-800-241-4141. *HML

Customer is complaining about the inconvenience of unavailable first class seats and asking is there no value of purchased tix. Agent informed that customer has no value remain to apply for first class and further informed about the service charges amount and said that comfort+ seats are available.
### Instruction: Below is a conversation between a human and an AI agent. Write a summary of the conversation.

### Input:
user: I was wanting to look into possibly upgrading my seat (GINX36) but the seating chart says 1st class and delta comfort are all gone. That's impossible.
agent: Hi Freddie, thanks for contacting us. My apologies for the inconvenience. One moment while I look into this further. *HML Thanks for your patience. I'm showing First Class is sold out for your flights; however, Delta Comfort + is available. The Delta Comfort + cabin is sold as a fare for this market; therefore, in order to confirm Comfort + there will be a difference in the fare. *HML
user: What does this upgrade list mean? And this one for the first leg of the flight?
agent: It looks like there may an error between our system and the app. I'm checking into this now. *HML
user: ive heard about airlines blocking out seats for the purpose of overbooking and juggling to squeeze profits. I didnt know you guys were still doing that or doing it period
agent: Thanks for your patience. I am showing seats available in First Class; however, the lower First Class fares are not available. Once your reservation is changed to the First Class cabin, you will be able to view and assign seats. *HML You may see more availability closer to the time of travel. *HML
user: This explanation sounds very convoluted. 1st there was no seats available, now there are seats, but there are no more lower 1st class fares available? What's does that mean and how do I upgrade seats. That's the whole reason I tweeted you. Cmon Delta aka *HML
agent: Freddie, in order upgrade your ticket to First Class, you must pay the difference in the fare. In reviewing your ticket, you have no value left to apply towards the cost of the ticket to upgrade. *HML If you're using miles to upgrade, the cost is 35,000 miles each way and you must be booked in a L, U, or T class fare. *HML
user: What do mean I must pay the difference but then say I have no value left in my ticket? Why not just tell me how much it is to upgrade like I've been asking from the beginning? What does it mean I have no value in a tix I purchased?
agent: To make changes to your reservation there is a change fee of $200.00. Your ticket is less than the change fee; therefore, there is no value in your ticket. I can provide an estimated cost to change your ticket; however, this does not include taxes and fees. *HML The estimated cost is $1,500.00 for First Class on your flight from EWR to GCM. This does not include taxes and airport fees and fares are not guaranteed until purchased. Please contact our International Reservation specialist at 1-800-241-4141. *HML

### Response:
Customer is complaining about the inconvenience of unavailable first class seats and asking is there no value of purchased tix. Agent informed that customer has no value remain to apply for first class and further informed about the service charges amount and said that comfort+ seats are available.