Hello Tmaz24,
Thank you for using Apple Support Communities.
I see that you are having issues with sending/receiving texts from one particular user. I would suggest taking a look at the following article for suggested troubleshooting:
If you can‘t send or receive messages on your iPhone, iPad, or iPod touch
Specifically the following section:
Sometimes your messages won't send to a particular contact, or you might have issues with group messages. For example, you might reply to a group conversation and receive your own message. Or you might get a new phone number and see your old one listed as a recipient in an existing group conversation.
Delete the conversation* that has the issue and start a new conversation:
- Open Messages and look at your list of conversations.
- Swipe from right to left on the conversation you want to delete. Then tap Delete.
- Open Messages, tap
, and enter the phone number or email address of your contact or contacts.
- Write a new message and tap send.
Best regards.