Is it possible to unlock an icloud locked iphone 6?

I've seen these sold o ebay and online there are companies that claim to be able to remove an icloud lock so the device works just like normal

https://www.officialiphoneunlock.co.uk/activation-lock-removal.php?aff=mach3

Is this possible?

or will it affect the iphones functionality/services/features/3g/4g in anyway?

No. ICloud lock is a security device designed to prevent theft. If unlocking was that easy, more would do it and there would be more theft. Since the lock and remote wipe have been made available to iOS and Android, theft has gone down. It remains a problem because some folks don't lock their phones or think the lock can be bypassed.

If you purchase a known iCloud locked iPhone and the seller can't unlock it, chances are high that the phone was stolen - which means you would be in possession of stolen goods. This means that if Law Enforcement chooses, they can confiscate your phone and you lost the money you paid. Just because the phone is locked does not mean is can't be tracked. As soon as it is turned on, the phone will connect to available Wi-Fi and send location information over the air… If the *real* owner set it up correctly, they will receive notification that the phone has been located along with a map location.

Well it depends, I don't think you yourself could unlock it, but usually you can temporarily bypass it to figure out the Apple ID which is their email. These tutorials are on YouTube, I don't think there's a real way to actually get into it and keep it unlocked without the answers to the security questions and password

Those companies that claim that are just scams