Worse customer service experience

Worse experience ever I did lay by and it happens that today I took out the lay by today and there is a item that I'm no longer interested on it and I see nothing that I can take at the shop they refuse to refund me the amount of that item they told me I must take something that is equal to that amount it's for the first time hearing that and I've asked the lady before making payment that can I able to return something on this lay by for refund she said no with no advice of what must I do before settle the amount on lay-by