You are welcome Shin, I have since checked and MPAS do have an online tool to check your supplier. MPAS is for your gas supply. To check your electric supply there is an Energy Network Association search tool. You check by postcode who your network is and then that network will have all the details of your current supplier. They should know your meter serial numbers etc. Please don't worry about it because if Octopus did take your supply back in July then you will ignore the letter from BG. If it turns out you were still with PE and now transferred to BG, you can still switch back to your preferred Octupus Energy. Although, the advise is not to switch straight away, because for a certain period of time whilst this crisis is going on, any credit balance is protected. If you do an immediate switch, you are putting any credit balance at risk. You will find all details about ways of finding your supplier on the Ofgem website. I hope the lines aren't too busy, maybe best to check online. All the best.