Thanks for posting in the Apple Support Communities iercan,
The following information and steps should help you prevent further messages from the number.
From the Messages app, open the conversation, tap the contact at the top of the conversation. Tap the info
button, scroll down, then tap Block this Caller.
You can also add a phone number or email address directly to your Blocked Contacts list in the Settings app.
1. Add the number or email address that you want to block to your Contacts.
2. For phone numbers, go to Settings > Phone > Blocked Contacts > Add New. For email addresses, go to Settings > Mail > Blocked > Add New.
3. Select the contact that you want to block.
When you block a phone number or contact, they can still leave a voicemail, but you won't get a notification. Messages that are sent or received won't be delivered. Also, the contact won't get a notification that the call or message was blocked. When you block an email address from Mail, it goes to the trash folder. Email blocking works across all your Apple devices.
Enable your settings to block spam phone calls
Block phone numbers, contacts, and emails on your iPhone or iPad
If you continue to receive messages from the same contact, we recommend that you contact Apple Support for further assistance: Get Support
We hope you find this information helpful!