Poor service from Groupon

Received delivery of items (bookshelves) purchased online. Only received planks and a assembly manual - no fastners. Followed up 13 January 2016 and they apologised and provided 2 options. Either return the product or purchase fastners for which they will refund me. I did the latter and sent them the invoices and requested refund on 25 February 2016. I have not received any reply.