I encountered this with GoneBingo.
They gave me a £5 free offer & with that i won £140.
I ended up playing through the slots & got the balance to well over £350.
Tried to make a withdrawal of £350 but this was rejected but only £250 was then available.Their reason for this was "because i tried to make a withdrawal on a win derived from BonusBucks the original £100 was non-refundable"
.
Anyhow i played on the bingo/slots for the next 8-10 days met the turnover requirements & withdrew a grand total of....................
£140
