Storage Heater not working after Smart Meter installed

I had a smart meter installed 2 weeks ago and since then my storage heaters and immersion element to heat up the water in a big cylinder tank are not working anymore. Both only run on off peak electricity. I have raised this with OVO, an emergency engineer, a commissioned engineer, came but couldn’t solve the problem. Since then I’m daily on the phone with OVO but nobody is able to help. I’ve raised a complaint, got a call from OVO and was told that my case is being looked into and I would get a call back. Nobody was ringing back. It’s very stressful to call daily, explain the same problem each time and not getting anywhere. I was even told by one operator that it’s my problem and not OVO’s.. It’s absolutely outrageous that an organisation like OVO is not able to rectify the problem. I wonder if someone had similar experience and can give advise how to handle the matter. Thank you