Appalling service when I want to upgrade package

I contacted Vodacom in October to upgrade my package from Smart S to Smart M - more money for Vodacom so you'd expect they'd be interested! NO! The first call centre person said we could do it all over the phone and confirmed the package would be changed 1 November. WRONG! She didn't know I had to sign a form for this to happen! So when the package wasn't changed on 1 November I called the Call centre they told me this. I tried to lay a complaint about the first agent but the useless supervisor (now the third person I was talking to) PROMISED to send me the complaint form but nothing. I completed the required form to move to the new package and EMAILED IT 5 TIMES to Vodacom!!!!!! Its now 1 December and STILL NO CHNAGE. What the heck!!! If this cannot be rectified I WILL CANCEL my contract even if it still has a year to run! WHAT APALLING SERVICE!!!