NO RESPONSE TO COMPLAINT

I bought a voucher from Groupon which the supplier did not honour, and I need to get a refund / credit from Groupon. I have tried to email & call for 2 weeks, but no one gets back to me. The time waisted with the supplier & trying to get hold of Groupon is shocking, and to not even acknowledge daily emails, is not acceptable. The complaints telephone line cuts off so this isn't an option in terms of trying to contact the company. I would like to try and get someone to respond the complaint & advise next steps to being re-imbursed