Please proofread this for me.

[Unregistered]

"I thought they have the right to ask for service they pay for
and naturally I have the duty to do a service for their satisfaction."

[2006]

"I thought they have the right to ask for service they pay for
and naturally I have the duty to do a service for their satisfaction."

How about this: '(I think) they have the right to receive the service they pay for, and (naturally)(of course) I must provide that service to their satisfaction.'

[angelg]

This way makes perfect sense to me:
"I thought they had the right to ask for the service they paid for
and naturally I had the duty to do a service for their satisfaction"

[tedtmc]

The use of 'think/thought' and have/had depends on the context.
You could say 'provide a service'.
And it is 'to their satisfaction'.
not a teacher