Ongoing issues with British Gas

daverave7

I'm looking for some advice with an ongoing billing issue with British Gas - they have now informed me they have started debt collection - despite them not supplying my gas since last May.  I have had three seperate calls/texts with them over the last few months, after each one I have been assured that my account has been closed.  The debt collection letter arrived on Xmas eve and this is the final straw - I feel that I am getting harrassed. Who (except British Gas, as they don't listen) can I complain to? What are my rights?
I've dug into a timeline of events, which I have summarised below, which might shed some light on the issues:-
November 2019: I used Cheap Energy Club (CEC) to change both Gas and Electric Supply from Pure Planet to British Gas
April 2020: When asked to input my latest meter readings, there was no option for Gas.  I checked CEC, and it stated that the switch was still in progress. So I then contacted CEC, who told me that the switch to British Gas had not been successful, and for me to do a new switch through CEC.  I did so, and moved both electric and gas to Tonik in May.
June 2020: I get an email from British Gas, welcoming me to my new home - I can only assume that this was them catching up with the switch I initiated in November 2019. I then phoned British gas and confirmed with them my meter readings at each switch.
July 2020: I receive a bill from British Gas for £220, which I paid. I checked the statement online, and it tallied with the meter readings supplied at each switch. I then assume that I won't hear from them again.  
September 2020: I recieve a text from British Gas, saying my bill was now overdue - but with no reference to any bill.  I called the number and spoke to a customer advisor who checked the national supply database and could see that they were no longer supplying my gas.  He apologised and said my account was now closed.
November 2020: I received a new bill for £126, but with no reference to the dates this corresponds to.  I tried to check the statement online, but couldn't as my account/log in is no longer recognised. I raised a complaint online.
December 9th 2020:  I received texts from British Gas, relating to my complaint. They claim that they are still supplying my gas.  I checked the national supply database myself, and it is showing as Scotting Power (who took over from Tonik).  I further complained to British Gas by text, and they replied and apologised that this had not been dealt with.
December 22nd 2020: I received a new bill from British Gas, this time for £117, and covering the dates from November to June (but no year stated). I still can't access statements online. The date for payment is January 4th 2021.
December 24th 2020: I received a letter from British Gas, dated 16th December, stating they are starting debt collection in relation to the £126.

I'm at a wits end with this, and just want it solved.  British Gas aren't listening, so I want to know who I should contact before a debt collection agency get involved?

Robin9

A formal written complaint - don't phone.   

Streaky_Bacon

As Robin says, a written complaint. I tend to use the Resolver website, but you could use email, or letter (get a certificate of posting). 
You have a good timeline, which you should include.
Make sure that you clearly state the resolution you require and tell them that they must put any debt collection activity on hold until the complaint is resolved. 
If not resolved in the required time frame, then you can escalate to the energy ombudsman.