Cant update

[Poloace]

Your current software version isn't supported . Vist a service center. 

Keep getting this message ever time I try to update phone.

[Temywealth]

Visit a Samsung shop. That could be fixed ,the software might be crashed or virus detected. They could install you another software if possible plus if your phone really worth it.

[Poloace]

I've only had my s20 plus afew months? So why won't it be worth it?

[Temywealth]

Would advise you should visit Samsung shop.

[Glenntech]

Did you buy the phone new from a reputable supplier, or second hand from somewhere else?
Have you had the phone long?

Maybe worth clearing the Partition Cache of the phone.
Should be straightforward

https://www.t-mobile.com/support/devices/android/samsung-galaxy-s20-5g/wipe-cache-partition-samsung-...

Have you tried backing up your data and doing a factory reset?
Going to a Samsung Experience Store could be a good idea, as they will be able to tell you what has happened, or fix the issue.
If all else fails then if you only recently got the phone, maybe worth going back to the supplier

[Pugs1957]

Hi, what is your current baseband version? Go to settings, about phone, software information to find it. While there also let me know your service provider software version.

[Poloace]

Gf got me phone of website called onebuy