Pathetic customer service

So Vodacom, for the 2nd time in as many years, has randomly decided that my account is in arrears. I have a debit order on my credit card. Works fine month in month out, year in year out, but every now and again this! So, I call on Sat, and the agent promises to get a manager to call me. Needless to say, no call. Then I call yesterday and choose option 2 for a call-back, because I've already been on the line for a long time (they are experiencing high call volumes - seems to be a common occurrence - don't you staff up for that?). Again, needless to say, no call-back. Billions in profits, but can't even get elementary customer service right.