From what I understand, You bet on team A and the bet changed after you went back to the site and you refreshed. First of all the only way to prove what you are saying is a screenshot showing you betting on team A which is something you do not have so your best bet and if you are 100% sure that you did bet on Team A is to try to talk with them but again I do not see them doing anything because without solid prove anyone can just bet and claim that the bet changed.

There is a big chance that you just miss understand the betting options and bet on the wrong team.