I have got a bill from my previous electricity supplier

it’s been 3 months since i switched to bulb. I am still getting bill from my previous energy supplier. is there a number I can contact on bulb?

Yes, click “Help” and the number is at the bottom of the page.

But surely you should be contacting your previous supplier about a previous billing issue? If it’s just one bill, and not recurring, is this not your closing bill? Does the listed meter reading match the opening reading you gave Bulb?