If they accepted the payment, which they normally do within 2-3 days you might be waiting a while for your refund. Their policy is to issue refund by check which takes upwards of 30 days. I found that out hard way as i cancelled on a friday and was told by one of their employees the check would be mailed the following week, i found later it can take up to a month.
Good luck
A cheque is a weird way to do things... Why not just send it back on the same card like everyone else?