[ehch]

I'm not sure how this is even working. I had my friend over about a month ago and he was going to buy old iphone 4 (only so he could play fallout shelter). Anyway he stuck his sim in to see if it works, but the phone was to slow anyway and couldn't run fallout shelter, so he didn't end up buying it, removed the SIM.

Iv recently been using it again this week for music, airplane mode on and wifi on. And started receiving texts from his brother, only his brothers side of the convo. so i called up my mate today and asked him, and he had been receiving only some text ( he thought his brother just wasnt replying) and the others went to me.

How is this possible, I have the phone on aeroplane mode and there's no sim inside ?❓

[Λlex]

This happened to me too. The messages I sent to my friend were also sent to his girlfriend's phone because they share the same iCloud account. (I am talking about iMessage.) This might be your problem too. Make sure you're the only one who's using the particular iCloud account.

[angrymcdouble]

Probably iMessage, restore the phone and configure it with your information only.
You can also just remove the iCloud account and unactivate/activate iMessage in Settings.app