Dealing with Import Declaration Errors made by Courier Companies

We imported some goods from Poland using UPS. The sender in Poland declared the value at 17,150 PLN, which is about £3,375. The parcel was delivered in December. We inquired about the import documents, but UPS answered that it was entered as low-value, so no import declaration was done. We thought perhaps the sender declared a lower value than on the invoices, so we contacted UPS Poland, and they confirmed that the full value was declared by the sender and all the correct documentation was submitted by them. We contacted UPS UK to ask for a post-clearance amendment but received no answer for over 3 months. We contacted the HMRC helpline, and we were told to just account for the import VAT in the tax return. Our accountant asked if, just in case, I could get that in written form from them, so I called them again the following day. I spoke to a different person who told me that the advice given the day earlier was incorrect and we could not account for it in our tax return. This is very confusing. What can we do in this situation? Any advice?

Hi Tomasz Sas,
You require either C79 or PVA statement to account for import VAT on VAT returns.
If full import declaration was not submitted by the declarant and importers EORI is not used on the declaration then C79 or PVA statement will not be produced. 
Check when you can account for import VAT on your VAT Return on below link.
When you can account for import VAT on your VAT Return
You still need to raise this with UPS to correct the import. Post clearance amendment team can only make non-revenue amendments belfast.pcateam@hmrc.gov.uk
More information on voluntary declaration available on below link.
Apply for a voluntary clearance amendment (underpayment) (C2001)
Thank you.