Thank guys. So I am just going to pay the original £20 that I owe and ignore the rest. Just out of curiosity why should I not phone them. Have I done more harm than good now that I have contacted them?

Hi Guys. Sorry if this has already been addressed but I am just looking for some advice. I purchased some items from Usa before Christmas and they were delivered via Fedex and they covered the customs and duty charge. The problem is they didnt tell me or inform me they had covered it so I didnt know I owed them money. I got a letter from Control Accounts Plc yesterday stating that my debt has be passed onto them via Fedex because despite previous letters I have refused to pay my customs and duty charge. The thing is I never received any letters from Fedex regarding these charges. The original charge was £20 and they are now trying to charge me £61 as Fedex have added on a late payment fee. I contacted CAP today and told them that I am happy to pay the £20 that I owe because that it a customs and duty charge however I will not be paying the latepayment fee as I never received any warnings or letters from Fedex. The lady on the phone was less than helpful and extremly rude saying that it was my word against theirs that I never received a letter as it was sent in November and they would be charging me the £40 no matter what. I explained I would pay the £20 and she said pay it but we will still be coming after you for the £40. They dont have my name only my Business name. What should I do? Should I pay the additional £40 or leave it and let them chase me. I know its only a small amount of money but its the principle. They have threatened the usual in the letter that it may lead to a Claim being issued in the County Court. Any advice would be appriciated D x