I work in telecoms for a bank.
Ofcom are really tightening up the rules regarding 'CLI'.
Larger companies, such as mine, are permitted the ability to spoof the caller ID. This is so that somebody from one location can visit another location and still send their correct caller ID - e.g. a Glasgow user visits Manchester and makes a phone call that still displays their Glasgow number to the call recipient. This ability requires a contract to be signed with the telecoms provider stating that you'll never send a caller ID that doesn't belong to the company. If you break the agreement they can immediately terminate all telecoms provision (that would be a really massive event for a bank).
If somebody is spoofing your caller ID, they are in breach of ofcom regulations. No legitimate company would do this.
I'd contact your phone provider and explain what's happened. They will be able to check their call records and hopefully prevent it happening.
I used to work for a major telecoms company ('a licenced operator') and their systems could trace calls end-to-end. If your number is hosted by, for example EE, but a call using your caller ID originated from another company (e.g. Colt), they should be able to see that happening and request the other telecoms company take action to shutdown the fraudsters.
As I've previously suggested, it could be an accidental configuration error. If that's the case, the telecoms companies would work with their customers to resolve it.
Personally, I take it very seriously in my role. I have put in hundreds of hours to take the bank from a position where we were sending out 'junk' CLI (and relying on the telecoms companies to simply change that to 'withheld'), to one where every single call is sending the correct caller ID and can be traced back to the relevant end user (even if the call recipient sees the caller as Private or Withheld, the caller's information is visible to the telecoms providers).