Re: Letter to the customer
I was under the impression that "revert" was Indian English. An American would say 'Huh?"
This is an EXTREMELY formal letter. A typical American letter would say "If you have any questions, please don't hesitate to call me either on my cell at 1234566 or on my landline at 23456680."
We tend to mock things written in a way that refers to the sender as "the undersigned." You don't want any personal contact and are not intersted in foming a relationship with the person when you call youself "the undersigned."
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.