Issue with text messages on iphone 4s?

So i've had this issue for a while and if someone could give be even a little bit of info, it would be much appreciated.
So, Over the past year, i have had an iphone 3gs, a samsung galaxy s3, and now i have an iphone 4s. The reason everytime that i got a new phone was because randomly, my texts would just stop sending, like it would just say "message send failure" and i couldnt receive texts either. I also couldnt get or receive calls. I have realized that this started happening when i started texting my one friend, it only happened when i would text him. I proved this by texting him from my moms phone and texting noone else, and the same thing happened to her phone.
i'm just wondering what could be wrong with his phone that is doing this? It only affects my phone, everyone else he texts doesn't have a problem. Hes with telus so could be bring it in and ask him what's up?

Are you sure your contract has not expired

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