Took money off my account without my authority for a returned shipment done 5 months ago

Parcelspot debited my account without my authority for a surcharge on a shipment done 5 months ago.

Received no prior warning besides a vague email the day before, which had very little info. When I queried it, I was first told that my shipment weighed more than what I gave ( It didn't as I weighed this myself ), then because it was returned to me they advised that the cost to bring it back was X3 more than what I paid to ship it.

When this was returned 5 months ago, I asked about the costs, but got no reply. I have taken this up with them and pointed out thew above, but they don't seem to care.