Device management

See this Apple article: Checklist: If you want to see if anyone else has access to your device or accounts

Checklist: If you want to see if anyone else has access to your device or accounts - Apple Support

See point 5.

I pay for my phone,

The question is -> where and from whom did you buy the iPhone?

Ask the seller who sold the iPhone to you if it was a business iPhone.

Then that person need to contact the company, and unlock the restrictions.

If it doesn't work, ask for your money back.

To keep your Apple ID account secure, see the following Apple articles:

Manage and use your Apple ID

Manage and use your Apple ID – Apple Support (UK)

Recognize and avoid phishing messages, phony support calls, and other scams

Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

Phony "tech support" / "ransomware" popups and web pages

Phony "tech support" / "ransomware" popup… - Apple Community

Identify and filter junk mail in iCloud

Identify and filter junk mail in iCloud - Apple Support

If you think your Apple ID has been compromised

If you think your Apple ID has been compromised - Apple Support

Identify legitimate emails from the App Store or iTunes Store ->

Identify legitimate emails from the App Store or iTunes Store – Apple Support (UK)

Set up iCloud Keychain

Set up iCloud Keychain - Apple Support

Create a strong password for your Apple ID, It is best if your password consists of eight or more characters and include upper and lowercase letters, and at least one number. You can also add extra characters and punctuation marks to make your password even stronger. 

Never provide your password, passcode, security questions, verification codes, recovery key or any other account security details to anyone else. Apple will never ask you for this information.

See also the following Apple articles:

About the 'Trust This Computer' alert on your iPhone, iPad, or iPod touch

About the 'Trust This Computer' alert on your iPhone, iPad, or iPod touch - Apple Support

Authorize or deauthorize your computer for iTunes Store purchases

Authorize or deauthorize your computer for iTunes Store purchases - Apple Support 

Get a verification code and sign in with two-factor authentication

Get a verification code and sign in with two-factor authentication - Apple Support

I have been having so many issues with all my apple products. My passwords are always changing , and it feels like someone else is in control of my phone and iPad… sounds like calls are being monitored, money is missing on credit cards and most recently someone has applied for a loan online. When I look to see what devices are connected everything appears fine…. I don’t know what to do this has been going on for a year now.

Same thing Is happening to me