Incorrectly charged

Hi, I terminated my contract with Vodacom at the end of July. I gave them my one months notice, expecting my contract to terminate at the end of August. I moved to a new provider mid August. In October, R2500 came off my bank account by Vodacom and I’m battling to resolve this. I’ve been passed around and now asked for evidence that I terminated! I’ve had numerous calls on this, not sure why they can’t just listen to the calls. Quick to take money, not quick to help resolve and refund. Am fed up!