Bad customer service

Am so dissapointed with MTN, i have contract with them of 22GB for R198 a month and now they are giving me 8GB for R245 a month and thats not the agreement and i sent them email no response and i went to branch i was told they can't assist me as contract was done online i couldn't understand. MTN is ripping me of now as they sold me lies and i ask for call retrieval as i have the call recording to back up my story but no one is willing to assist me