CRS debt collector chasing for gym debt that's not mine

Hi all

Can anyone help / advise?

CRS are chasing me for £400ish for a gym debt. Not only do I not live in the county where this gym is, but I've never even stepped in a gym! (I'm also a member of Slimming World groups online, unsurprisingly).

I've responded to a few emails and they insist I'm the person they're chasing. However the only 'proof' of membership was an email that they've forwarded on. It just seems dodgy because the email address they have is mine but I don't delete emails and I don't have that.

I've called their line and they refuse to speak with me because I can't pass security - because they don't have my address right and because I never took this membership out. The person who writes the letters apparently does not take calls.

So... My questions are:

1. This isn't showing on my credit file. Can they now make it appear? The alleged debt is from 2014 and this is the first I've heard.

2. How can I resolve if the call center won't speak with me because I can't pass security and the person writing the emails doesn't take calls?

3. Is there a way I can formally complain to an ombudsman?

Thanks!