Not Happy With After Sales Service-There is none

I placed an order for a pair of flats Order No 39140, unfortunately they are too big, I normally do take a 7 in Crocs, but for some reason these are too big. The Crocs were delivered in good time, but the problem now is I have sent numerous emails trying to exchange for a smaller size On the support mail. To date I have not had one response, tried calling the contact no. Permanently rings. The after service is definitely not up to standard. Spoke to someone on your chat line, was helpful in saying will exchange but that's where it ended. Impossible to communicate like this