I doesn't appear that they have any sort of ongoing phone survey. You might want to call them up and tell them about this so that they can warn their customers. I suspect the caller might have ended up trying to switch your supplier part of the bill to whichever company was calling.
We finally bought a phone that can block calls and this number was put on the block list a week earlier. Today we got seven calls from this number to our phone in 25 minutes. Our phone will ring once and then block the call.