MTN CUSTOMER SERVICE

I have emailed the customer service last week to email me my paid up letter they sent me an email to direct my query to which is *** i have sent 2 email already the is no response. Despite the several email I have tried to reach their contact centre 2 days in a row no response. 1st day i hanged up the call after an hour of no response. Today i gave up 2hrs 5 minutes holding on the line without getting any assistance. HOW TO REACH THESE PEOPLE?