Sorry to hear you’re struggling to get in touch with them. I don’t have any contacts that I could get in touch with; however, the questions you want to ask them are the sort that they will make sure to communicate with customers if and when such a merger happens.
Rumours of mergers can take ages to actually come to fruition (if ever at all), so it can feel like ages before you get any details as a customer. However, legally, they do have to provide you with information once contracts etc are signed for a merger to go ahead – so you won’t be left behind wondering what’s happening. They’ll write to all of their customers, at least by email and/or text, and usually in a letter as well, because they must notify people of any changes to their contracts (i.e., who their provider is/changes of name etc).
So, while I can’t help directly, I can say not to worry – the merger was confirmed in May 2020, but the paperwork and actually getting it sorted can take a very long time to sort out. As a customer, they’ll definitely get in touch when all the details are clear!