I don't mean to sound alarmist but alarm bells are ringing here - and it's really important that you separate the debt problem to the new scam problem.
Stepintochange is a scam, they have placed Google Ads on the search 'Step Change' to find vulnerable people like you.
They are not trying to steal from you now, they are trying to steal from you in the future. The information they've given you will allow them to open bank accounts, take out loans, start phone contracts and more in your name - they are just waiting for your credit to be good again.
If you haven't already, speak to Action Fraud who will be able to advise you on how to protect yourself, given what you've given away. I am really sorry - but this is really really dangerous.
I only know this because someone used my bank details to open phone contracts earlier this year and they helped me resolve the issue. That was really damaging, stressful and time consuming - and all the scammers had were by sort code and account number.
Stepintochange have all of your details. Change all your passwords. Speak to every business you mentioned to them. Most importantly, speak to Action Fraud!
I hope it all works out ok 