Who installs electricity smart meters on behalf of OVO?

My smart meter is not sending readings automatically. I have been waiting for several months to have a new one installed and today received a garbled voicemail about booking an installation. Hooray! However I couldn't hear either the number to call or the name of the company “acting on behalf of OVO Energy". Does anyone know the  contact details or name of thecompany who does this work for OVO in the London area? (I have tried OVO customer services but couldn't get through.) Thanks!