How do I eliminate system admin application permanently on my Android phone

My friend registered on an app with my phone to get a loan from the PalmPay application. The management asked him to install an app before the loan will be given to him, they say the application will be for the assurance that the loan will be paid back, and the security plugin application was installed on my phone as an admin application. He has paid back the loan but now I think someone is using the application to have access to all my details. I decided to remove the application, but I can't permanently delete the admin application from my phone before they do something very bad with my phone. They are already on my Facebook account/Instagram account. They are trying to get more from me. I can just restive a message from Amazon and other important platforms that I usually keep my money. They are trying to reset my password to all. Please, I need help to protect my Android phone from them. Please, I really need help before they do something very bad and wicked to me