Changed tariff without permission and overcharged.

[Vealy]

I'm already an O2 pay monthly customer but purchased a Mate 20 Pro on O2 refresh with a rolling contract with the intention of cancelling it immediately.
I rang the next day after receiving my phone to terminate said contract which was agreed. The next day however I was signed up to a new 24m contract without my knowledge or permission. There was no mention of a new tariff whatsoever during the chat.
I immediately rang customer services who immediately terminated the contract. However he terminated the contract on the new tariff (which I didn't agree to sign up for) and now have a princely bill of £391!!

I rang complaints who tried to sort it out. They told me they would adjust my bill but only the following month as this month's bill has been generated. They told me to cancel my direct debit on the meantime and to put it back on when next months (adjusted) bill will be sent to me.

Is this the correct procedure? Will I get cut off for cancelling my direct debit, albeit temporarily?

[MI5]

@Vealy 

You need to CALL customer services as live chat have badly advised you already, they will likely screw it up even more for you.

202 from your O2 phone or Guide: How to find help & contact O2 

[Vealy]

I rang customer services. It was the advisor on the phone who told me to cancel the direct debit instruction.

[viridis]

Well of course they put you on a new tariff,
They upgraded you in order to get the mate 20 pro you asked for.
How else did you think you'd be paying for the mate 20?

[Vealy]

The mate 20 Pro is an additional contract. Not my existing one. Phone was paid outright and was on a monthly rolling contract.

[viridis]

Oh wait, so you paid outright for the mate 20?
That makes sense that they messed up

[Vealy]

Yeah. The mate 20 was paid outright and on a rolling contract. I wanted to cancel the rolling contract but they signed me up to a 24month contract for no apparent reason whatsoever. Which is quite worrying TBH.

[MI5]

Regardless of the mess up, I wouldn't be cancelling my direct debit.
A bounced DD will just result in O2 sending the debt collectors round and giving you a black mark on your credit score.
You need to get back onto CS to sort this before the DD is called from your bank.
@Marjo @EmilieT @Martin-O2 any help here please?

[Vealy]

I agree, but it's £391 extra I can't afford right now.

[Martin-O2]

Hey @Vealy we can get our Guru team to take a look at this for you. I'll send you a quick private message so I can get some details. 

@MI5 Cheers for the tag.