IMessage Issue

Hi, I’ve been having this strange issue for a really long time and I don’t know if it’s just my carrier that has been acting up or it’s just the iPhone itself. I have this problem when I want to send a message to an Android user, my message would immediately not go through and would say “not delivered”, I would click the “not delivered” option to resend the message, but it still wouldn’t go through. When it comes to verification in apps that uses a phone number, I never see the message at all and it never appears because it’s an outside user and not an Apple product. I found out that the only users I can message are users with an Apple product, it sends with no problem. The same thing happens with group chats that involve Android users like I don’t see their texts and only see the Apple users texts only or even the group chat doesn’t show up because there’s android users. I used to never have this problem and I could text everyone freely, but now I can’t even text people with an Android. Is there something to fix this? I’ve tried everything from completely resetting my phone and turning on and off my IMessage, nothing seems to work.