The Manager,
My name is _________ (name) and I am holding a vision insurance policy from your company bearing policy number __________ (mention policy number).
I am writing this email in order to inform you that I am willing to upgrade the insurance policy from _________ (mention plan) to __________ (mention plan) and for which, I am willing to pay the required additional amount and proceed with the formalities required.
Please guide me through the procedure and I shall be highly obliged.
Yours truly,
[Digital Signature]
____________ (Signature)
____________ (Name),
____________ (Contact details)