Got my cracked iphone screen replaced and now my phone has a mind of it's own.

It will select anything at everything at random, I'll text somebody and it will type random letters and send. Or The swipe up/down menus will come up/down and stay. I've liked, unliked, unfriended, unfollowed and sent gibberish to several people and it's very irritating. I can still use my phone to text/call people, but I have to fight with my phone in order to do so and have to deal with sending gibberish along with every message I send and even to people I never intended on texting. The only way I can get it to stop what it's doing and let me use it is to shut my screen off and turn it back on but that method still isn't very effective.

Also I sometimes see several vertical lines going down the length of my screen. They don't move or anything but I'm sure it has something to do with why my phone is acting out. And well my question here is what should I do?