Switched from GiffGaff (02) to Lebara (Vodaphone) the other day. Started to notice that my battery was running down really quickly. It lost about 18% overnight without being in use at all. I've done all the usual checks, Bluetooth off, Background App refresh off and a host of other power saving things. It's not the phone battery as I've been experimenting putting the sim in an older phone with the same results. With the sim out of the phone and wifi on there is no noticeable battery drain. We have excellent Vodaphone signal here, better than O2. I'm interested to hear if anyone has the same problem and if they have remedied it.