Hi, I have filed my tax return as Single for the year 2018, but i need to change it to married, could you please let me know the charges for it. My India num - [phone number removed]

This is a public Internet forum.   For your privacy and security you should remove your phone number from your question.    No telling who might try to phone it to scam you.    To edit it you should have a small icon just to the right of your question.  Click that, and there should be an Edit selection in the dropdown menu.   It's also possible a Moderator might remove it in the meantime.

Did you use TurboTax to prepare the 2018 return you filed?   

What is your citizenship status?   Are you a US citizen or resident alien for tax  purposes, or are you a non-resident alien?     When did you first come to the US and how long were you here?   What type of visa?