Excess Mileage 22K over when VT

[Guest]

When i recently called to VT my agreement, the man on the phone stated that there was an error on the contact and that there was no mileage stated on the agreement i signed. I have gone over the mileage by 22K miles, im due to pay 5.9pence per mile so around £1400 from me, however im not sure how to move forward with what the agent at BMW told me with regards to an error on the documents. So do i simply state this when they come asking for the money and state that the agent told me i wouldnt have anything to pay?? Any ideas what it could be he meant when he stated there was an issue with the agreement and that i shouldnt have to pay anything?

Thanks
Mark