Early exit charge still showing after I cancelled due to move

Hi all, I'm hoping someone from Nexora can explain this because I'm a bit fed up now. I cancelled my broadband when I moved out at the end of April. I was told there'd be an early termination fee because I had a minimum term left, fair enough, but the final bill has come through at £143.20 and the online account now shows another charge pending for £12.74. I didn't even use the service after 28 April. Why am I being charged again? I rang and got told different things by two people, one said it was the full ETF, the other said it was a pro-rata charge. It doesn't make sense. If anyone knows how Nexora calculates this, please let me know. I'm not trying to dodge paying what I owe, I just want it to be right.