Was hacked ... Help!

Hi! I recently traveled to the Middle East ... while there I was given a relatives phone but with a new phone number to use and my own phone was sadly linked And hooked up to my relatives phone ... after a while I realized she was recovering a copy of all my incoming and outgoing SMS, emails, WhatsApp and Insta correspondences on a separate 3rd party Apple Phone of her own ... she lived in the same house as I was and we shared the same WiFi ... anyhow I am back in Canada now and trying to figure out what I need to do to ensure my phone and all apps are no longer compromised. Some believe changing passwords is enough but I was told in the Middle East that once someone has access to your user names and passwords ... even when you change them later, they can “over ride” it ... and some Apps like WhatsApp doesn’t even have a password to change. Sorry for the info overload but something about my Find My Phone always is auspicious to me as well because whenever I fiddle around with my phone and change passwords, an “disabled” message comes on? Thought to throw this all out there for you technology wizards ... I’m just thinking I have no choice but to get a new phone number, SIM card and even worried I may need a new phone even though I know it has nothing to do with the phone itself 🙈... Help! Please 🤪😏