iMessage and FaceTime number expiring soon reinsert SIM

I am in the UK and recently received the above message. The phone is an iPhone 15 with two esims, a local UK one and a US AT+T one. The message relates to the US number. I have the cellular service for AT+T number turned off as it costs $10/day and I intend to be in the UK for several years. I am going to university in the UK.

What should I do? I cannot actually reinsert the SIM as there is no physical SIM on the iPhone 15. If I turn on the AT+T cellular, I will get charged, which I would like to avoid.

Any help would be appreciated.

Thank you!

Brytan