I’ve meant to have transferred to Bulb with USwitch at the end of last month but I haven’t received anything and the bills are still going to the previous occupier of our property
There are several issues here.
When the previous occupier moved out, they should have notified the energy supplier and gave closing meter readings. If they are still getting the bill in their name then it sounds like they haven’t done this.
When you moved in, you should have contacted the existing energy supplier and given your opening meter readings. If you’re not getting billed by them in your name, then it sounds like you haven’t done this.
Did you take care of the moving in issues before starting a switch of supplier? If not that could likely be why it hasn’t worked. You need to arrange with the existing supplier to pay the bill from the date you moved in. Only once that’s done can you start a switch.
If all of that has been done, then you’ll have to contact Bulb customer support (rather than this community forum) and ask about the progress of your switch and whether it even got started.