Poor service delivery from One-Day-Only

I recently bought an item from One Day Only website. It was the Crossley Soundbomb Boombox. On receiving the item, it worked for 20 minutes on battery power after which it just switched off by itself. Initially I thought that it was faulty or uncharged batteries and I switched over to transformer power. Once again it worked for 20 minutes after which it just switched off by itself. I contacted customer services at one day only to try and exchange the product but to no avail. I have on several occasions over the past two weeks tried in vain to contact one day only and to exchange the product but no seems able to help me. I have never had such poor service delivery from an online company. I would not advise anyone to purchase from this company. I will not make use of them again.