DHL
Quarantine processing fee

Hi 2 weeks ago i received a parcel from my mother in the UK, it contained 9 packets of Bisto gravy powder. Now 2 weeks later DHL have sent me a bill for $47.30 for Quarantine processing fee for a package with a value of less than $20.They tell me that i have to pay this i myself have had no dealings with DHL before receiving this bill so how can i be liable to pay? do i really have to pay this.