MTN CONTRACT CANCELLATION IMPOSSIBLE - SOMEONE PLEASE HELP WITH THE NUMBER OF THE CEO

My son who has moved to the UK is trying to cancel his already expired MTN contract. He has mailed them , has a receipt reference and a reply mail saying they will contact him within two days, which is 11 days ago. I cannot get anyone to even talk to me to provide the correct information on the procedure to cancel - he cannot phone as it will cost him more than a pound a minute to hold on, and we all know how long MTN keeps you on hold. They are so so eager to tie you up into a contract, but it is damn nigh impossible to cancel a contract.