Not my fault but stuck with no service

I upgraded in January 2015, to a Huawei E5220 3G Modem at Freeway Cellular, Lenasia and requested the data usage be capped. In August 2015 I received a bill for R3128, 86 and stopped using the modem completely. Despite this I received a bill in September 2015 of R****, 11 for the same device. MSISDN *** validated URL's and twice consultants validated the charges. I could not validate most URLs and some didn't even exist. I complained to Mr Khan at the store as well as to head office as by December my lines were barred altogether. Mr Khan claims he can do nothing and head office - Lesego - claims the store can pass the credit because they acknowledged and confirmed that I requested capping. To date head office is awaiting evidence that the store did cap so that they can pass the credit. Who's lying? It makes me feel like both parties are passing the buck. Meantime I'm stuck and continue to pay the monthly subscriptions on all four devices with only incoming texts and calls and no voicemail. My psychology service is compromised and the inconvenience is unspeakable. The truth is, my 20 some odd years patronage and loyalty to Mtn amounts to nothing. Totally unacceptable.