Not getting messages from certain android phones

I just started using an unlocked iPhone 8plus and I can’t get my phone to receive text messages from certain android phones. I can send my messages to any phone just fine, but I cannot get a response unless they choose on their phone to send the message as an sms. I can’t seem to change anything on my phone to fix this. All of my settings are set correctly to send as sms, sms tuned on and mms turned on. My phone number is checked under iMessage as well. I have reset the phone, changed out the SIM card and everything it seems. Anyone had this happen and found a fix? My carrier cannot figure it out and I can’t find anything else to try.