Q: Random text messages

It appears that somebody was able to sign into your Apple ID and has used your account for iMessage. Change your Apple ID password immediately.

If you think your Apple ID has been compromised - Apple Support

Look in your contacts list. And if it is being obnoxious, block their numbers. Send a message saying, "Who do you want to reach? I think you got the wrong number." And it appears you are using imessages which has nothing to do with your phone carrier, but you can be contacted by your phone number or your email if you set. Just tell them they may have gotten the wrong number. Probably that is the case.

Usually these types of occurrences aren't true hacks, but rather that your password and email/username combination is somehow known. If you use the same password on multiple accounts, and one of your accounts isn't through a secure service, someone may gain access to all other accounts where you use the same password. Another thing I should add is that if you have other accounts associated with the same email as your Apple ID and you used the same password for those accounts, you should create new passwords for these accounts as well so they don't become compromised. It is best practice to have unique passwords for each account. I am guilty of reusing passwords, but what I do to minimize risk is use unique passwords for the most important things, such as email, Apple ID, and online banking. I don't necessarily do this for trivial accounts that don't expose personal information or for those that I can just easily create another account if necessary.

This has nothing to do with hacking either. Most likely they got the wrong number or email. I once got text messages from someone in Nevada (I have no friends or relatives I know who live in Nevada). And if you contact TESCO, they can't help you.