Refurbished iPhone asking for another Apple ID.

So recently my mom purchased a refurbished iPhone 7 for me from an online seller. The problem is I am unable to download some apps directly from the App store.

Whenever I turn off/shut down my phone, it prompts me that I have to login with someone else's Apple ID to be able to use the App store properly (Download new apps). Ironically, the Apple ID it asks for is my mom's old Apple ID from when she used to work in her old company, which is quite strange since she has never touched this phone before so I'm not even sure why it asks for that information.

Does anyone know how to solve this issue or remove that old Apple ID since she no longer works there nor has owned this phone before. Thanks.