MTN not Responding

My data on my MTN contact disappears every month before the load new data. I've written to *** 5 times and IF I get a response, they send me a standard email asking for my ID, PIN and bank details. When I send it to them there is again no response. My reference numbers are #*** and #*** Trying to phone them is an impossible task as there is no answer. All I want is an explanation on where my data goes, because as far as I know it is against the law not to carry forward data not used.