You should respond to the notices to cure in a timely fashion, and contest the debt, following the procedure outlined in your co-op's governing documents. Include proof of the account error as well as any relevant communications you've had with the board or your building's managing agent.
If the financial dispute gets to court, the burden of proof will be on the co-op to show that it is properly charging you. You'll have an opportunity to respond to the co-op's claims and provide evidence of the errors.
Collection
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