This scam involves council tax, where people are getting cold-called about the chance that you might be in the wrong band for council tax and that the company ringing you, will sort it out for you, for a price. Naturally, if you need a refund on your council tax, you can query it for free yourself, and your local authority should sort the rest out.
The scam asks for your bank details, and £65 to cover admin costs and the processing of the refund itself. This is a nonsense and you should tell these companies where they can stick it. Once you've hung up on them, you should then report the company to Action Fraud, which you can do by clicking here. Or, if you'd prefer to ring someone, call 0300 123 2040.
If you do have a problem with your council tax band, and want to make a challenge, then you can do it completely free of charge by getting in touch with your local Valuation Office Agency (VOA). The website can be found here, or you can ring 03000 501501 (England) or 03000 505505 (Wales).