Can I go to an Apple store for removing activation lock for my iphone?

No. The Apple Stores cannot remove activation lock. That is all done via the form online and with proof of purchase.

However, there may be other ways to resolve your issue.

Are you logged into any other Apple devices using the same Apple ID? If so, go to the settings, your name at the top, click on password & Security and "change password".

If not... you can try account recovery by going to iforgot.apple.com and start the process.

How to use account recovery when you can’t reset your Apple ID password - Apple Support

If you aren't able to do any of those, then use this article to start an activation lock removal:

How to remove Activation Lock - Apple Support

You are most welcome. If it was denied it's usually because the documentation you provided for proof of purchase was not what they need. Maybe check with where you purchased it from for a better proof of purchase. It needs the serial number, name of business, cost, and device listed on it.