Beware of buying from Mango South Africa site

I recently ordered 2 items from Mango's South African site only to discover that Mango expects me to fill out a custom clearance form and to provide a copy of my identify document. The requirements for these were not disclosed at the point of sale and I would have expected Mango to clear customs and not to make it my problem. Mango's customer service refuses to cancel the order as I am unwilling to provide my ID and I'm stuck in a chicken and egg situation where I have to clear customs to be able to return the items. Mango has taken my money but has not delivered the good or service that I contracted with them and I therefore believe it is in breach of contract.