iPhone is being accessed remotely and sending messages
Inform your lawyer immediately. If you don't have a lawyer, get one now. It is essential that what is happening is documented. Law enforcement (your local police, constabulary or gendarmerie) may be able to assist if you are being harassed.

If you can afford to purchase a new iPhone, even a refurbished 5s without all the extra RAM &amp; whatnot, do so. Create new email &amp; iCloud accounts. Use a password manager such as LastPass, any two-factor authentication available and turn off the old phone.

To block your Caller ID information from being displayed temporarily for a specific call: Dial *67. You will need to dial this for each call you want to block. Enter the number you wish to call (including area code).
Tap the Call button. The words "Private," "Anonymous," or some other indicators will appear on the recipient's phone instead of your mobile number.