The reception in my house is supposed to be good indoor and out for 4g but I struggle to make or receive a call indoors. I used to use wifi calling with EE and it was great for my needs. The smart talk app is a buggy mess and every time I update it it seems to get worse.
Yes I am in the same boat, have to leave my phone in the window to get any signal, works fine outside. My Mrs is nearly out of contract with Vodafone but I am reluctant to move her to BT until we can get a better signal indoors.