A Vat Return question, please help

Dear All

I am running a small business for a year, my business nature is providing business services to non-eu base companies. Recently I have one request but I am not sure can I take it or not.

A non eu base online shop ask me to provide a payment services to their company in UK, which is making payment to Royal mail and some couriers payment, then I can charge a small percentage of service charge monthly. As the online shop expects the postage cost will be deduct the VAT cost, my concern is can I get back the postage VAT return to cover the full postage I pay. Could someone can help me please. Thanks