Vodacom ****ing with my money

I bought an Ipad in 2015, my contract was due for an upgrade this year. I was only left with one month of paying the old contract which then included the upgrade fee. I upgraded to their 10G data without taking any device. Now, the debit order for that one month got through in April 2017. then came May 2017 Vodacom deducted again, I enquired by calling their accounts department, only to find out that Vodacom says I took out a device and that I have 3 more months to pay, but their system and contract says I had one month remaining to pay. I have been paying the new contract money for the 10G. Now vodacom sent me notice to pay R1,316.00 within 7 days. I can't get through to their account department because they barred my numbers.