old apple ID comes up on new phone, how do I erase old ID?

Check the App Store and iTunes Store to see if there are any updates for apps/purchases. A request for another Apple ID password is often caused by updates to apps/purchases that were made when using the other ID. Those purchases are tied to the other ID and can't be transferred. One option is to delete the apps/purchases made by the other ID and download them using the new ID if desired. After deleting the apps, it may be necessary to restart the device/computer before you can download the apps again. If necessary, check your purchases history to see which apps/purchases weren’t made by the current ID. 

Purchase History Review.  *

Or you can try to set up Family Sharing  between the IDs to keep access to your purchases.

Family Sharing.      

ASC YouTube for Family Sharing   

Family Sharing - Set up.        

How do I erase old Apple ID.my I pad always show my old Apple ID