Dubious repair quote??

I've been a fan of Ryobi and their machines for a long time. Always got great service and fair prices for repairs and new purchases. BUT... Recently brought in a brush cutter for repair as it would not start as a result of fuel flooding. After got a assessment for the repair. Was told that a piston , debris and heat shield , spark plug etc all need replacing because of damage due to incorrect fuel mix? When queried how this damage related to the problem I brought it in for ? Have still not had a believable technical response. Have tried with several mails to get a answer. The spark plug I replaced myself just recently. The fuel mix story is a a fabrication. i mix the fuel myself using their measuring container. Very disappointing.!!