EXTREMELY BAD SERVICE

My name is Hofman, with Vodacom account number: I***9. I am not sure if Vodacom is a legit service provider or a bunch of ********. A few weeks ago I received an sms informing me that I owe Vodacom R313 and I need to make a payment on the said amount. I have not made the payment on the above amount as requested by their collections agency (VVM). Today, all of a sudden I receive an sms claiming that my services will be de-activated if I don't make a payment of R706 on the very same account that owed R313 just a few weeks ago. I tried calling VVM on several occassions today but to no avail. I would like to know how come that I can owe R313 and just after a week or two Iam told that I owe R706. Where does the R706 amount come from all of a sudden, or am I being ****med here.