Mora creditoris

My contract for Data bundles expired, then I went to one of the Vodacom shops to ask for Data bundles contract only, a sim card contract for data bundles, I am R100 per month, I did not sign any documents for that, now the problem is, I am paying for nothing because the signal in this area is very bad, I complained about it before but things are still the same, this is a breach of contract, and I want to be out of it, I am not enjoying the benefits of this contract. as per my understanding of the contract, I have 2GB to use during the day and 2GB to use during the night every month, but this is not happening, and Vodacom does not forget to enjoy the benefits of that contract, this is a one way benefit thing, I am being ****** every month as I am not able to use their data bundle as much as I want as per the benefits of the contract. I suffer loss financially and educationally as I could not submit my assignments online due to Vodacom, I then de-registered my modules due to that. Who can pay for something and not use it. Last time I spoke to Mpo from Vodacom call centre and she gave me a very bad attitude about my complaint. I want to be out of this, This is MORA CREDITORIS