Closed mobile account - but they still want money

Mosquito46

Mobile phone company Three maintain I owe them money. I maintain I do not.
In September last year my need for the Three accounts ceased.  I phoned Three up and said I wished to cancel and what would I need to pay for this.  The agent did some calculation and gave me the figures.  I was told that this was for full and final closure of the accounts. I took that to mean that any period of notice was included. How I wish I had noted the agent’s name and the time of the call!  On 12 September 2019 the amounts were paid to Three and I thought that was the end of it.  I assumed that the accounts had been cancelled because that’s what I asked the agent to do.  That’s why I paid the large amount of money on 12 September.
In October I got a bill from Three.  Thinking this was an administrative error I pointed out the accounts had been cancelled in full.  But in November I got another, and another. Each time I contacted Three to explain.  Later bills I sent to their payment section which does not seem to talk to their customer service section.
In January 2020 I got another bill for £49.  Remember the accounts had not been used since early September so I was puzzled by that. I again informed Three that the accounts had been cancelled and closed in September 2019.
In February I received a letter saying my contract was due to end in March 2020 and asking if I was looking to cancel the contract!  Why did they think I had paid several hundred pounds in September? The letter said they would close the accounts on 19 March 2020 and then I would get another bill!  Sure enough, I did, this time for £86, which again I sent to the payment centre asking them to stop.
Now Three have involved a debt collection agency, PastDue. But as you see, I did my best in September to do the right thing and pay off the contracts so if there was a shortfall in what their agent told me, then surely that is their liability?
I have raised a dispute with PastDue and sent PastDue this statement of my case.  Should I stand my ground or offer a part payment without prejudice to make them go away?  If so what should I offer?

dazzaofdagenham

My advice here, and I had problems with 3 before..

Pay them the amount they want....get the debt collector off your back and in case they start destroying your credit file.
then document everything you have said and send it recorded delivery to them.

maxximus75

You need to raise this with Three as an official complaint so they have to investigate.