TVS company - Two wheeler Service issue

I have given my two wheeler for service on **th jan-**** in TVS service center at attibelli bangalore-******.

Early they told ***Rs for service cost for spare, later they told through phone call it will take approx ****rs for service due to engine sound rising.

I given confirmation for service below ****rs Only.

After completed the service they rise the bill around ****Rs. I got shocked while see the message from TVS on **st jan.

At the time i went to service center they told *****. Rs need to pay for service charge including GST.

I didn't agree for this much of amount for service.

I didn't get any intimation for this expense. And
I didn't give any confirmation as well.
I didn't receive proper intimation message as well.

I need justice for this issue. They are try to cheeting.