The logic is that VM bill in advance, basically they bill/invoice you for February in January and so on. Fine.
"However, I have now received a further bill for the continuation of my package from 27 Feb - 14 Feb” I assume that is a typo and should have read 27th Jan - 14th Feb, fine easily done. You cancelled giving the required 30 days notice and have had acknowledgement than your service will terminate on 31st Jan (well today), yes?
Now VM work on the basis that you might not cancel (not sure that anyone ever has, but still) and decide to stay right up to the last minute - so their billing system carries on assuming that you are still a customer until the 30 day period is up and they get the message that you no longer want to be a customer.
This can be further complicated by the fact that the ‘billing date/cycle’ doesn’t always correspond to the contract term dates. So it seems like your billing date starts on 27th of each month, so on 27th Jan you are still a paying customer so they bill/invoice you for the following month, fine.
What should happen (whether or do it does is another matter), is that on 14th Feb, you will be billed for a full month (27th Jan - 27th Feb), but then get a refund by cheque (yes I know, how quaint) for the period 1st Feb to 28th Feb.
Look don't blame me, I didn’t set it up, I just know how it works.