I had a similar issue with the whole free offers fiasco.
I signed up to an online bookmaker promising 4500 credits. And yes said credits were not given.
I contacted the bookie only to be told it's WGTs problem and if WGT contacts them they might listen it's a huge con.
I've contacted WGT and as of writing they haven't bothered to respond
my advice would be to steer clear of such offers