I'm concerned that my phone might have been hacked

Keep the iPhone updated to the latest iOS always and never Jailbreak. That's it.

iOS / iPadOS devices cannot be hacked or infected with Virus / Malware / Spyware if it is updated to the latest iOS/iPadOS unless you have intentionally downloaded spurious software or unauthorized apps directly from the internet and installed on your device or/and have Jail Broken. 

It (Hacking) also depends on how careful are you in sharing sensitive and valuable information pertaining to your iPhone such as Passcode, Password etc with your friends and family members.

Be careful when sharing the device's sensitive and valuable information with friends and family members.

Thumb Rules:

1. Enable  Guided Access before handing over an iPhone to kids
2. Don't share Apple IDs
3. Don't Jail Break
4. Don't share sensitive information pertaining to your device and payment methods
5. Beware of Phishing

In order for a key logger to work it first needs to be installed on your phone.. if your phone isn’t jailbroken there’s little chance of that. This sounds more like someone is attempting to scare you into performing an action or divulging information that you otherwise wouldn’t.

If you believe that your Apple ID credentials have been compromised, then change the password to your Apple ID.

Open Settings ➔ Apple iD (Your Name at Top) ➔ Password & Security ➔ Change Password.

Axel F.

I’m under the impression that the hackers have a key logger. So they can get your new password also. I’m up against a group of ppl, I’ve recently learned that one of them found a hacker that guarantees them access to my text ,phone calls ,contacts, etc. my newer contacts are gone from my phone as of about a week ago. What can I do? Please help me