Refusal to refund payment for out of stock item

On the15th of April l ordered and payed for a FLOOR LAMP BASE at Maanica.com.On the 22nd of April l was told the item was out of stock therefore l should send them my banking details for a refund,which l did.Their lines are always busy l can't get through to them.I sent them numerous emails requesting to be refunded but up to now l haven't yet received it.They keep on creating tickets and times for payment that they do not honour.l have proof of payment for my order and all correspondence from Manicaa.