How do I stop gamesonmobile being sent to my mobile fone its costing me heaps and I donknow how to stop it?

I made the stupid mistake of texting to games on mobile to send space invaders to my phone. Stupid me asumed that it was a one off thing and that they would send the game and that was it but Im getting several a fortnight and have been for 2 years. I dont know how to make it stop other than getting a new number which I dont want to do please help me