My partner and I bought 2 interrail tickets for 7 days only to realise that we only needed 5 days. As suggested on the interrail website, we bought our 5 day pass and requested for a refund of our 7 day pass. It has been over 2 weeks and we STILL haven’t had a reply from customer service although they said they would reply within 48 hours. We are owed approx £600 which they were very quick to take from us and are very slow to refund.  In these difficult times, money like this is very important. 

Does anyone know any other ways to contact customer service to chase this up? 
I want to avoid a formal complaint but should they delay our refund much longer I see no other option.