Unable to pair an iphone 7 with an apple watch series 4. Need ideas...

Hi, I own an iphone series 7, with up to date ios for it( 15.8) works great and not looking to update at the moment. But I purchased a series 4 apple watch after checking that it was compatible with this older phone. This is a refurbished watch that look like brand new and appears to function properly.

When pairing, my phone gives me the message "iphone out of date. This apple watch requires a newer version of ios". Now, I cannot do anything with the watch because it has not been paired with this phone, so I cannot pull up any menus on the watch to verify the watchOS for it. It seems strange that the watch and phone are compatible by any info I have found, but tells me I need to update. Any clue what I am may be doing wrong?