It is not uncommon for a contract dispute to arise if a team or player feels the other party is not upholding their end of the bargain. If you have an agent, they should be the one handling your contract dispute. This is one area where a licensed agent or attorney is likely to give you significantly more protection, expertise, and support than an unlicensed agent.
If your contract has a BAT clause, which is very desirable from a players perspective, then you or your agent can file with the Basketball Arbitral Tribunal, which is an independent and FIBA recognized conflict resolution body. The BAT will hear your case and come to a binding decision. Filing with the BAT involves a fee which is dependent on the specifics of your dispute. The amount of this fee should be weighed against the significance of your case as the benefits of having your case heard may not outweigh the cost.
If your contract does not have a BAT clause, it is less enforceable and you are granted significantly less protection. In this case, your dispute will be resolved in the local courts of where you play. It is not uncommon for cases of this sort to sit unresolved in the local courts, leaving players with no recourse in the event of a contract dispute.