So you are sure that you are not the owner of those accounts indicated in the email? 

Is really something suspicious are happening with sportbet.io? I have seen recently there is a couple of accusation are active here and this is another one. If op is not a owner of those accounts then how he prove it(may there is no way to prove it from user end). But sportbet can present the investigation result here to prove op is lying. I know sportsbet is a reputed gambling here but since there are 3 cases are discussing recently, maybe something wrong happening with sportsbet users.