Adding Bulb Gas. Have Electricity already

I have Bulb for electricity which is great. I’m coming to the end of my gas tariff with nPower and want to move my gas to bulb as well. However there doesn’t seem to be a way to get a quote and add the gas. Everything is electric only or dual fuel switching. There’s no option to add my gas. Also there doesn’t appear to be a way to contact bulb and discuss this.