Misleading game rules and bad customer service

I draw magic wheel total 97 draws but it give 65 magic cores . At magic wheel rules it says 20% drop rate for magic cores. Actually it drop rate is 13%. So, I ask their customer service, their reply is wearied. They say about matchmaking but I asked about magic wheel drop rate and I can't even reply . They close session.

THAT drop rates and customer service reply are Normal? What is your experience about magic wheel drop rates