contract changed

i phoned AutoPage on the 7 May 2015 to tell them that i am not continuing with my Blackberry phone as it was about to end the following month, they put me through to the guy his name is Diane, he convinced me to stay because i told him i saw Samsung Galaxy Trend Neo plus at Cell C for R159, he said they have the same phone and i will pay R160, since i took this phone i find myself calling their call center *** and these consultant are rude sometimes and they refuse to put me to their manager, i have been billed for BIS and other things that i don't know and now the premium has gone from R179 to R250, i will take legal action now cause this is frustrating.I pay R250 for only R110 air time and 25 SMS.