My SE blocks other’s texts to me!

I have an iPhone SE 2020. Several weeks ago when texting a friend that I have always texted, she started getting texts during the thread saying she had been blocked from texting my number! I do not see these messages in the thread, but now she cannot text me although I can still text her. This has now happened with four people. I have come to realize that these four people all have androids that use Verizon towers. I have no problem with other iPhones or with a friend who has an android that uses I think, T-Mobile.

I have Straight Talk and my phone uses AT&T towers. I have checked to be sure these numbers were not accidentally blocked and also did a network reset. I cannot figure out why this has happened and wouldn’t have know if my friends hadn’t called to tell me. Thanks for any suggestions.