chaning contract without my signature

When nashua closed down it went to vodacom. The contract i had was an open line contract at 135.00 per month, 75 min 100mb data and 50 sms per month and a recurring 500mb data montly on the contract. When i came close to the 500mb monthly i would receive and sms to say data usage warning. Never had a billing issue etc with Nashua. First month with vodacomand i get a bill 0f 1400.00 . They said the billing was correct!!!! they dont have a data limit on this phone. I asked them to putt a call limit on the phone as they told met that they cant add a data limit. Firstly how is that correct if that is not the contract i had with Nashua????? . set the call limit at 50.00 as we user more data then phone or sms. 2 days later i get softlocked i phone and they increase the limit to 150.00 and remaining mb was 591. 4 days later i get an sms to say softlocked again. firstly i wait for 25 min for someone to assist. now the tell me that i have a NIGHT Owl( data only to be used at 12 to 5 am) on this line(490mb remaining). HOW IS THAT POSSIBLE???? THAT IS NOT THE CONTRACT I HAD. PLEASE SORT THIS OUT. I WILL CANCEL THE DEBIT ORDER AND TAKE THIS FURTHER. YOU CANT CHANGE A CONTRACT WITHOUT MY AUT