Help! StepChange vs. CCS vs. Tesco Mobile

Hello! I’m hoping someone can point me in the right direction here because I’m having a bit of a nightmare with CCS and Tesco Mobile.

I had a TM debt which went into my DMP with StepChange. StepChange were sending the payment to CCS and have given me proof to show the cheques were cashed and not returned.

CCS say they’ve been sending the cheques directly to Tesco and Tesco say they haven’t received any payment since February this year despite StepChange confirming they paid CCS and CCS saying they paid Tesco.

As far as Tesco is concerned, I owe over £200 and they say I have to pay that and sort out the missing money with CCS. CCS have been very unhelpful every time I’ve spoken to them but have provided receipts showing they received regular payments from StepChange and are adamant they passed them on.

So two questions:

1) How can I escalate this and find my missing money?
2) My credit file states that I’ve missed payments between February and now but I haven’t. Can I get this amended as I can prove I have made payments? The only payment I have technically missed is November because I was trying to pay the debt off in full (a balance of approx £12) but Tesco had to investigate it and took ages getting back to me and then couldn’t give me the correct figure because of CCS’s error so it wasn’t my fault that I couldn’t pay when I was offering to?

I’m being passed from pillar to post and not getting anywhere so any advice would be greatly appreciated.