Cannot send or receive text messages with new iPhone 18 to android phones

Help! I recently switched my mobile service from Verizon to Xfinity and upgraded my iPhone from a 13 to a 16. Now, I'm unable to send or receive text messages to any Android phones using the new iPhone 16. I've upgraded to iOS 18 and followed the instructions to activate the RCS feature. I spoke with Xfinity both in person and through online chat, and they confirmed that Xfinity supports the new RCS feature, yet it still doesn't work. This issue is occurring on both my new iPhone 16 and my husband's, so I know it's not a defective device. I've also done some research online, but I still can't find a solution. Can anyone help me with this issue?