MoneyGram Unfair Currency Exchange Dispute

I went to E**** Ç*****, located on Gaziantep Gaziler Caddesi, to collect money sent via Moneygram. However, they're converting Euro to ₺ at a rate lower than the current market rate. While the Euro price is 30.38, they're paying at 29.90. When asked for a receipt, they refuse to provide one. Who oversees such businesses? Is there any regulatory authority? My expectation from Moneygram is to revoke their representation rights for this establishment. If you doubt my claim, you can send money to your account and check it yourself.