Visa type

Hello,

I want to change my visa type on my letter to 1 month single entry instead of 1 month multiple.
I have paid $20 by mistake instead of $16.
Can I get a single entry $25 visa on 1 month single entry visa type?

Also, my date of travel is tentative. I could travel on 20th or 21st of December but I have chosen 20th December as my date of arrival.
I hope that will not be an issue.

Please let me know as soon as possible. Thanks!

Regards,
Yatin Khaneja