Random contacts are appearing in my contacts, some are old friends, some I have no idea who they are. I have made sure that contacts from apps like Facebook and Linkedin, are not allowed to be synced. I thought that might be the end of it but no. A new contact appears on my phone with disgusting messages (redacted by IconDaemon) in the mobile number. I have a picture to show. I have deleted these contacts off my phone but can anyone help?
Open the contacts app and tap "groups" in the upper left. This should list all potential sources of new contacts. For instance, I only have groups listed under "iCloud" and "Facebook". If you see a source that you're not expecting you might be able to narrow down where these contacts are coming from.
It might also help to restrict what apps have access to your contacts and perhaps disable some. To check go to settings... privacy... contacts.