user: U changed my flight, I lose boarding position A to C &amp; wouldn't let me $ for priority boarding during check in! #poorservice
agent: Mike, in these situations, we're only able to issue the next available boarding position. Did you discuss Upgraded Boarding @ the Gate?
user: I did but was told they just sold the last position right before me. I ask to purchase it when I was checking my bag and was told I couldn't
agent: Sorry for the trouble, Mike. Upgraded Boarding is popular &amp; sells out fast. Fingers crossed for next time; see you onboard!
user: Why are we not allowed to upgrade our positron at the time of the change during luggage check in?
agent: Because we allow Passengers to easily make changes to reservations, we don't have an accurate count until closer to boarding time. (1/2)  As such, our Gate Agents have the ability to offer Upgraded Boarding when available within one hour of departure. (2/2)
user: That makes sense. Wish your check in agent would have explained it that way.
agent: We're so sorry for your continued frustration. We hope you will give us another chance.

Customer is complaining about the poor service where they changed their flight and lost boarding position A to C and wouldn't let them $ for priority boarding during check in. Agent updates that their Gate agents have the ability to offer Upgraded boarding when available within one hour of departure and apologies for their continued frustration.
### Instruction: Below is a conversation between a human and an AI agent. Write a summary of the conversation.

### Input:
user: U changed my flight, I lose boarding position A to C &amp; wouldn't let me $ for priority boarding during check in! #poorservice
agent: Mike, in these situations, we're only able to issue the next available boarding position. Did you discuss Upgraded Boarding @ the Gate?
user: I did but was told they just sold the last position right before me. I ask to purchase it when I was checking my bag and was told I couldn't
agent: Sorry for the trouble, Mike. Upgraded Boarding is popular &amp; sells out fast. Fingers crossed for next time; see you onboard!
user: Why are we not allowed to upgrade our positron at the time of the change during luggage check in?
agent: Because we allow Passengers to easily make changes to reservations, we don't have an accurate count until closer to boarding time. (1/2)  As such, our Gate Agents have the ability to offer Upgraded Boarding when available within one hour of departure. (2/2)
user: That makes sense. Wish your check in agent would have explained it that way.
agent: We're so sorry for your continued frustration. We hope you will give us another chance.

### Response:
Customer is complaining about the poor service where they changed their flight and lost boarding position A to C and wouldn't let them $ for priority boarding during check in. Agent updates that their Gate agents have the ability to offer Upgraded boarding when available within one hour of departure and apologies for their continued frustration.