I am late to it but let me make a guess.
The OP placed a bet, odd changed from 2.15 to 1.5, the accepted odd was 1.5 and the stake was $1000. But then OP lost the bet. You refunded the bet that was placed instead of making it a loss bet. If this was a winning bet then it does not make sense for OP to be happy with the refund only, he would needed his investment and the profit.
It's the other way round. The odd was 1.5 then it rose to 2.15 around about the same time OP was placing it. The system accepted the 1.5 odd instead of notifying him that the odds had changed. OP lost the bet, but he has been refunded the initial stake given system error which is fair enough.
Yeah I can see where I was wrong but the end result stills is in OPs favour, isn't it?
If the conclusion is the bet has been lost then no matter what the odd become the OP was not supposed to receive anything for the lost bet but he received the stake that he wagered. Or I got this wrong too?