Impossible to cancel an invalid data contract.

I called 3 times to try cancel a 24 month data contract I never renewed. I called in asking for proof that I renewed the contract. I was told someone else would have to call me back. Also, no-one would give me a reference number for my call. The 2nd person hung up the call. The third refused to help saying that the first person is meant to deal with it. I couldn't get reference numbers for any of the calls I made from anyone I spoke to, which is a first. Both time I was told I would get feedback within 48hours and never did. I can't register for an account because this is an old SIM card I no longer have. How am I meant to get to the bottom of this.