Hello, I have a apple watch series 3 and I don't seem to find the iphone its paired with and the apple watch is locked and i am unable to unlock and also cannot reset it. Please help

OK. I'll never understand why people change their Apple ID? Changing the actual Apple ID causes all sorts of issues down the road.

If you don't know the Apple ID used to set up the watch, you're going to need to find the original purchase receipt with the watch serial number on it and ask Apple to help you remove the lock. We can't help you with this.

See if this helps you --> How to remove Activation Lock - Apple Support

What do you mean you can't seem to find the iPhone it's paired with? If this is a used Apple Watch, if you don't know who previously owned the watch, it's totally useless to you. If you bought it, get your money back. If you found it, turn it over to the police. Or recycle it responsibly.

You're welcome and good luck.

Here's another tip. Get yourself a notebook and write down your important ID's and Passwords and keep that notebook in a safe location where you can find them in the future to help you avoid the pain this is surely going to be.