Suzuki Access 125 — Everyday problem in suzuki

Address:

380013

Dear sir i have purchase suzuki access 125
[protected] only 12226 km run

reg no. Gj01pa4796
1. Mileage problem
2. Every 3 month speedo meter verum problem
3. Rear break problem
4. In this monsoon lock and wiring burn
5. Last problem is very serious piston gone

last problem why piston gone at 12228 km.
I always make service and oil change after 1500 to 2000 km

please help for last problem because this change cost is 4000 to 5000 rs.