worst service in the world

i have a i-pad through MTN and over the past 18 months my account never goes over R350-00 a month then all of a sudden i get a bill of over R3000-00 for th emonth - i also have a 5gig wifi rooter through MTN - i have queried the account for 3 months and told MTN to sort out my query before taking money from my account in good faith i paid half the account without MTN getting back to me. - it has taken 3 months for MTN to get back to me and i am still no closer to ending my terrible journey with MTN - never have i witnessed such terrible , arrogant service in my entire life. all i get from MTN is this is your account now pay it - i have also asked for someone in management to contact me but still no 1 has bothered - all i want now is to find out when my accounts with MTN expire so i can move to vodacom