Review Extra charge without any invoice evidence

I have been order stuffs from UK for years (very frequently at least 3 times a month) never been charge for custom tax, but this time my parcel ended up by this company "Aramex". I got a call from this company on 26/10/2017 that my parcel have arrived in PP(I put delivery address in Siem reap in my order detail) and asked me to pick it up there. As my address is Siem Reap I asked if it is possible to send to the address that the sender put on the parcel(siem reap). The staffs said "yes ", but I have to pay 12$ extra for my "31" pounds parcel, which never happened before. She said 10$is for the custom tax, and 2$ for deliver to my actual address. I agree because I don't want to lose my parcel. Today27/10/2017, I received my parcel. I tried to look for the invoice, I found none. I called the staffs, she said she forget to put it, and said the company does not have the invoice of custom tax from the government , if I want the actual invoice from the government custom, I would have paid more than 10$, and there would be more complicated with documents (?)(it is just 2makeup remover and a lip gloss, not any sort of DRUG)She continues we charge you only 10$ because our company have a good connection with custom tax staffs(?). Does you company participate in CURRUPTION?
I just want to make sure if your company really does that or the staff wants to earn extra cash by using your company name.
Raksa Sovann