CLI from overseas is considered unreliable and it may not be possible to use this to identify a company with the relevant overseas telco. Furthermore, it may be of no value.
If the Silent Caller has no UK or EU presence itself and cannot be shown to be acting as an agent for a company that does, then this activity is outside the range of Ofcom's jurisdiction, which derives only from an Act of the UK parliament. It would appear that CRI is a US company.
The ICO has made some efforts, with limited success, to achieve cooperation from US authorities on some extreme cases that breach both US and UK regulations. There are however no formal international reciprocal arrangements in place, outside those effective through the provisions of EU treaties (whether or not constitutional in their nature).
The general situation with withheld CLI is not so bad as it may seem. Telephone companies are able to place a "trace facility" on a line. This enables the true CLI of identified calls to be stored and accessed. The caller's right to privacy prevents this information from being released to the public, however it may be released to "appropriate bodies". In 2003 BT was persuaded to add Ofcom to its list of such bodies, which previously had contained only the Court Service and the Police.
This was very helpful to me in presenting my first formal complaint to Ofcom and it also had a significant bearing on the initial investigations conducted by Ofcom. Ofcom however is seen to no longer conduct investigations in response to complaints.
For those who wish to take extra personal measures to monitor unexpected calls, to record calls and avoid being bothered by Silent Calls and calls from those unprepared to say who they are, it is possible to spend money on a device that does this job rather well -
www.truecall.co.uk. This is NOT "the answer" to Silent Calls, but it may be found to be of value to those who would like to have the benefit of a robotic personal assistant to take calls from unrecognised callers.
I hope this advice is helpful.
One would think that if they were unhappy with the response they received they would simply stop calling the same number as they had nothing to gain from doing so. They do not make money from simply being vindicitve. It may however be assuming too much intelligence on their part for any account to be taken of the reaction received.
I continue to recieve recording message calls from "the Debt Helpline" despite invariably speaking to an agent and asking for their full name and address, thereby causing them to hang up. The last exchange was interesting as the agent suggested that I review the provisions of the Telephone Preference Service. I was able to cap this suggestion by advising her to review the difference between the provisions of regulations 17 and 19 of the PECR.