unfortunately the physical ecocash mastercard dosent work online, yu have to generate a virtual mastercard then sign up for a payment mothod called Skrill (because virtual cards are not accepted because they have no account holder's name etc) also paypal cant be used for that!
within your Skrill account add the ecocash virtual card , now on on william hill choose deposit then select Skrill as your payment method follow instruc & done!!
and yes yu can withdraw your winning back to your Skrill account
with skrill.... minimum deposit $15 free to deposit and free withdrawalls
yu cn olso order Skrill's mastercad which yu can use for shopping online, withdrawing cash from local ATMs shopping in local shops where mastercard is accepted (free of charge) to create your free account at skrill go here https://account.skrill.com/signup?rid=60755158