iPhone Handoff Not Working

[u/ProcessOpen1370]

I'm trying to set up handoff on my iPhone 16 Pro and iPhone 12. Both devices are updated to the newest iOS. They're both on the same Wi-Fi. They're both logged into the same iCloud and it gives me the option to set it up on both phones but once I get past a couple steps, it comes up with this error message trom my carrier, which is T-Mobile saying that I should call them to finish setting up my watch. I have no clue why it's talking about a watch because I'm trying to do this with two iPhones. I talked to both T-Mobile and Apple and neither of them were able to help. I was wondering if anyone knew what this is or any way to fix it.