Solving any problem should start at lowest level so start with local manager, if that doesn't solve the issue or if manager is part of the problem then escalate to next level of management like a regional manager and all the way to corporate level... Find out who this restaurant chain belongs to online or ask them to give you a name and phone number and deal with that person...Hope this helps and pursue according to the criticality of your concern...
Call or go and talk to manager
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