Gosh we had exactly the same scenario.
Very toxic EW - my now DH had to take her to court to get access to see the kids or be able to phone them. She wouldn’t allow any contact / phone time outside of what was written into the contact order. He was only allowed to call the children 3 x per week at 6pm. If he phoned at 6:05 - the phone would go unanswered & a shitty message would follow saying he was late and wouldn’t be allowed to speak to them.
When the kids were 11 - dad got them mobile phones so he could contact them. The kids mum wouldn’t allow the kids to text or call dad but she would constantly text / call on dad’s contact time.
She was extremely persistent. When we were having dinner for example - we have a no phones at the dinner table rule. Mum would constantly call / text and the kids would get extremely stressed if they couldn’t answer. She would get angry if they didn’t respond / pick up immediately (and we are talking in excess of 6 calls per day on dad’s time when he only had them EOW. All this when dad was only ‘allowed’ to call on a Tuesday, Thursday & Sunday at 6pm.
Like you - this started to really stress me out as well.
We implemented a couple of ‘rules’
Phones on silent - if you missed a call / text, it was no big deal. And make sure you model this - if you don’t want to snow call you don’t have to and you can ring back at a time that suits you.
My DH & I don’t constantly carry our phones around. Model good behaviour - you don’t need to be glued to your phone.
No phones upstairs at night. Phones downstairs on charge. We’ve relaxed this now the kids are 15+
No phones during meals
Create your own boundaries and model them / stick to them. It does get better as the kids get older. I still remember the panic from my DSD when she was around 12 as she had 3 missed calls & 6 texts from her mum in 15 mins & she hadn’t responded. This is mums anxiety / control transferring to the kids and you need to manage it.
Good luck 🤞