How to tell if my iPhone is truly hacked?

In early May I received a text message from a fake number asking “Is this (username here)?”. Then never said anything until about 20 days later when they messaged me asking “what do you do”. I replied by asking who they were and they responded with “just someone who knows that you is hacked”. So I ignored it thinking someone was messing with me because until they messaged me from the same number on WhatsApp. I went and spoke to a couple guys at the Verizon store who ended up telling me I shouldn’t have anything to worry about since my bank accounts have been safe and no loans have been pulled out under my name or anything. Stopped receiving any weird messages for a good while until I downloaded Telegram and then got two separate messages on there saying “yo”. One from a different fake number and one was from a user account that said “”Feed The Nation” and had a photo of someone in baggy clothes pointing a gun at the camera. I read that factory resetting my phone would get rid of hackers so I tried it but then just a couple nights ago got a message on WhatsApp from the original fake number asking “you’re the dude who got hacked right” and then someone named Kima tried calling me twice back to back on WhatsApp as well the same night. When I did the factory reset, somehow it transferred only my contacts, some photos and everything in my notepad. I read someone recommending not to transfer any back up information but even though they got through the reset, have they hacked my phone deeper than that? Am I going to need a whole new phone and different number? I don’t know how the hacking stuff works. Even today my bank accounts have not been compromised, no loans, no weird apps have been installed or anything. So I don’t know what’s going on with this person who tries talking to me from time to time but makes me feel weird about using my phone sometimes like if I’m being watched. They don’t seem to know anything personal about me. Just one of my usernames.