***********/ misleading online shopping services

I have made a CASH payment , only to receive an email on the 9th stating that they cannot find stock . My dispute is the fact that they offer online shopping channels that are not update . They sell stock that they actually don’t have , now they have taken my payment and I am basically waiting for 17 days for my refund . I have emailed them 7 times and called about 5 with no joy Please can you advise a way forwards . I want my refund asap .