have data contract but i cannot use it,

am very disappointed with cellc, i have a data contract with cellc, but I cannot use my data, when I browse internet it gives me an error, signal is full but I can only browse internet if roaming on Vodacom but it is very slow , I called several times from January, and I was promised that a technician will be sent to look at the matter, after two months I was told that there is network upgrade in my area going on ,and no one is sure when the upgarde will be done, until today, so now I am paying every months for nothing, and I would like to know what do to, because I don't have cash to cancel my contract, since it is still on its first year, please advice, elvis, ***, lotus gardens x2, Pretoria west