Cancellation of a tablet that was not working

Tablet was not working i submitted to vadacare in february 2014 and i waited for three months in april, the manager told me straight he cant fix it, what he can do is to cancell the contract becouse he cant give me a tablet and i call the cancellation and retention while i was in the shop, he was told tp send and email for cancellation, i was suprise whn he gave me the print out of an email, he wrote, i requested an ealier cancellation intead of saying he failed to fix it and he sent it to midrand 3 time. within that three months i paid R1797 while the tablet was @ the vodacare, i have sent them several email they didnt respond i aproached hallo peter, still didnt attend to it, what they did thy blocked my mobile phone in october 2014 up to date but they are still sending me bills for a tablet that is seated @ vodacare for the past 15months. the tablet had a ploblem since day one of not conecting to the network couse it was the 2nd time it does that, on the 1st incident it stayed for 30days and i payed R 599 for that month while it was @ the shop. all in all the tablet only worked for 5mnths and i was supprised to find out they have blaclisted my name intead of replacing it.