Being charged after contract ended

[#1]

HI, looking for some advice. I moved my contract to Vodafone in July 24. The fibre supplied by Vodafone has digitial voice as part of the package. I received a text from plusnet when I placed the vodafone order, to say "sorry you're leaving etc". I just noticed today that I've still been being billed by plusnet £28 per month for line rental. 

I called plusnet today and they said Vodafone should have let them know they needed to cancel the contract, but also said "it's also our fault so I'll credit you a month of bill payment".

I've paid 3 months of line rental since the contract should have ended

I'm not sure who I direct my complaint to, is it Vodafone? However plusnet obviously knew I was leaving as they sent me a text back in June when I signed up with Vodafone

any advice would be helpful

thanks

[#2]

When I left Plusnet (FTTC and landline) and moved to Zen (FTTP with digital voice) I noted that as soon as the number port completed (within less than two hours of the fibre installation) my old phone number had changed ( I checked via plugging in an old phone to the master socket and dialling 17070). 

Therefore, if you were on ADSL or FTTC with Plusnet, as soon as the number port completed your account would be closed (as it was associated with the telephone number) and so Plusnet have no excuse for billing you beyond that date unless that date was within your 14 day notice period and only then for the balance of that 14 days.

If your Vodaphone service is provided over an Altnet then there is an issue that the systems may not have communicated properly with Plusnet (on the OR network) and so if the original installation date was changed from the one they obviously knew about as they sent the "sorry you are leaving" text Plusnet may not have been aware, But, as I said once your number was ported then the account would have ceased.

I would raise a complaint with Plusnet as they do seem to be in error.