Bajaj automobile - Service center issue

I have handed over my NS***
At Raj bajaj centre Reay Road,
Even if my bike was in operative situation the only problem in it was it used it get shut when switch from neutral to gear. And meter box issue
After sending my bike to Raj service centre i have been informed that the bill has been made of Rs.***** after hearing the bill amount i had complaint the issue to bajaj customer care regarding such amount of bill made
Such bill for only * years old ns*** is very much as they have purposely been added many charges without any major issue in the bike.
And they had not repaired the bike's speedometer display they are like it will charge more ****.
How can we trust such service centre for future service.