'Invalid' Tickets for Lana Del Rey

I booked tickets through 'get me in' in December for Lana Del Rey in May. Everything seemed good, I got standing tickets, which I wanted and the price wasn't too bad. I received the tickets within 2 weeks of booking them and they in sealed secure envelope. Everything seemed great! Things all went badly ONE week before the event. I got a call but I missed it but I had a voice mail from get me in telling me that my tickets for Lana Del Rey were no longer valid and that I needed to contact get me in urgently. I tried calling at least 20 times before I actually got through, to the AUTOMATED 'help line' after choosing my options to speak to customer services, I waited for 45 MINUTES until I finally got through. Baring in mind this is a 0844 number so costs quite a bit on a landlines! After finally getting an answer, the woman told me that the tickets I had ordered for my son to see Lana Del Rey for his 16th birthday were 'invalid'. They gave me a full refund but said there was no other tickets left of the same type. They also gave me an extra 50% refund to spend at get me in but why on earth would I want to buy from them again when they claim to 100% guarantee there tickets as being genuine!? They don't have an email address I can use to contact them to complain or dispute this so all round I am totally unimpressed and disappointed with this sham of a business!!