Cancelation of contract

I have sent numerous emails about canceling my contracts. I am immigrating next week and will not be using my numbers any more. I cannot pay for something,I am not even in the country to use! I have been trying for 2 weeks to sort this out. I have been a customer for more than 15 years with MTN and have never had issues. I am really disappointed that such a big service provider cannot help me with a simple task.