Remove old Apple ID

Delete the apps and download/purchase them again using your ID

You can't remove, delete, inactivate, close or merge Apple IDs. They're forever. You can just stop using them, but purchases with that ID will forever be tied to it. You'll have to purchase them again with the new ID.

If they are still free you won't have to pay for them - you will just need to delete the apps from your phone and computer's iTunes library (if they are in both places) and download them from the App Store on your account

What is/isn't free ? Updates to apps are free to download. If the actual app is now a paid-for download then that can happen, a developer can change things.

If those apps were downloaded by your friend's account then only his account can download their updates - all apps (and anything else downloaded from the iTunes stores) are permanently tied to the account that downloaded them. To get the apps linked to your account you will have to delete them from your device and download them using your account - if the apps are no longer free in the store you will have to pay to download them

Apple is like a big bank vault. Each Apple ID is like a lock box in the vault. You cannot mix up the lock boxes, so each Apple ID can ONLY have the stuff that was downloaded with that Apple ID.

Here's the deal: you have stuff on your phone that was downloaded under Apple ID #1. Now, you're using Apple ID #2. That means all the stuff that was downloaded under Apple ID #1 can no longer be updated or re-downloaded.

To make Apple ID #2 the one that you use all the time and to make it so that Apple ID #1 never pops up again, you'll have to make a choice: you can completely erase the phone and start over with Apple ID #2, or you can continue having trouble with Apple ID #1 popping up.

If you decide to start over, you can follow these directions: Use iTunes on your Mac or PC to restore your iPhone, iPad, or iPod to factory settings - Apple Support

If you decide NOT to start over, you'll have to put up with Apple ID # 1 forever.

Contact iTunes Support - if they can confirm your id and that it's your account they should be able to re-enable it. You can contact iTunes Support via the 'contact us' link at the bottom right of every page.