أنشئ حسابًا أو سجّل الدخول للانضمام إلى مجتمعك المهني.
accepting the mistake (if or if not),polietly suggesting him to the some other best thing.
talk to customer, sometimes they need a guy in suit talk to them in generous way. accept mistake, be calm and problem solving, say apology.
Complementary services, is the best one.