Being charged double for their mess

I upgraded my contract "early" which implies that I'll be paying for one contract. I was never told that I have to pay for both phones for one month.

Delivery says 2-7 working days, I got my phone after 13 working days. So they only activated my new contract in July when it should have been activated at the end of June at the latest.

I've tried talking to people in the Telkom mobile shops, they "don't know", the call centre isn't helpful, the online chat told me there's nothing they can do about it, I've requested a call back from a manager 10 days ago and I'm still waiting.

U don't feel comfortable paying for 2 phones for one month considering that it wasn't my mistake, they should've had the phone delivered in time and not charge me for 2 contracts for 1 month