Not being able to change classic gamertag without paying

No. There's no way around the charge. You'd have to pay if you want to change your tag.

I didn't recieve any warning of a gamertag change and I've had my previous one for 3 years. I would appreciate being able to change my gamertag for free without having to pay for something that I had no part in.

I changed my gamertag to "tosya" thinking that it would be "tosya" in-game, but it's "tosya7641" instead. I thought that the number would only be for adding a friend etc. like how it is in Discord. I wasn't informed that I would not have the gamertag
i picked. If I knew that I would have picked a different gamertag. I want to either change only my classic gamertag without paying for a gamertag change, or revert to my old gamertag.

The only way to change it would be to pay for it again. Unfortunately.

It's not possible to delete gamertags. If you wanted to change the gamertag two times you would need to pay 1,600 Microsoft Points (800 Microsoft Points for each gamertag change). So first you'd change the gamertag of SrTommy to something else, and then
you'd be able to change SrTommy1981 to SrTommy. It's not possible to do this without paying as gamertags cannot be deleted.

Without a doubt that gamertag would be flagged as offensive, You won't be able to get it back and to change your current assigned gamertag you would need to pay $10, Theres no way around the gamertag change fee after a forced gamertag change.