Yep call support and ask them to turn it off. I think it's partly luck if you get off first time, I had to call up 3 times. First call they didn't have a clue what interleaving was and went through a useless script. Second call they told me I had to turn it off myself on my router. Final call they sent me to sales even though I knew they couldn't help, to which I made it clear I wasn't going to get thrown around. I then was put through to very helpful bloke who knew exactly what to do and by the end of the week it was sorted. That was the last time I called support thankfully! not done so in years or I might have gone bald from pulling my hair out.
Maybe try email or even the BT reps here who seem very helpful?