Telecom regulator TRAI has slammed Anil Ambani-led Reliance Communications for "usurping" unspent balances of its mobile customers after its operations were shut down. Earlier, reports said that RCom has sought withdrawal of the regulator's directive asking it to refund the balances. Calling it "unethical, immoral and unjustified", TRAI warned of punitive action if the company does not comply.