Some companies that say they can prevent all nuisance calls claim that they'll make sure the call centres know not to contact you.
But companies making legitimate cold calls must already screen their outbound sales calls against the TPS register– it’s the law.
Which? has come across companies offering alternatives to the TPS, and claiming to be more effective than it.
But some may do no more than charge a fee for signing you up to the TPS - which you can do yourself for free.
Which? spoke to a number of major companies involved in the direct marketing industry. None of them use additional registers, just the one supplied by the TPS.
Another claim often made by companies who promise to stop all nuisance calls is that they can deal with calls from withheld numbers.
But BT told Which? that while it would be possible for the phone network to trace a call, a third party company - such as those promising to stop nuisance calls - would not have access to the information required in order to do this.
Alarm bells should ring if a company claims it's more effective than the TPS.
As explained above, companies making legitimate cold calls must already screen their outbound sales calls against the TPS register.
And Which? found no evidence of companies involved in the direct marketing industry using registers other than the one supplied by the TPS.
Some companies are claiming the TPS is selling your details onto third parties, but this is strongly denied by the TPS and there is no evidence to support such claims.
There is no global law. Call centres only have to screen their calls against the TPS list if they’re phoning on behalf of UK-based companies.
Some overseas callers are meant to screen using the TPS but they ignore it so these companies are unlikely to use a commercial register either.
Other overseas callers aren't legally required to screen their calls against the TPS which means they're not legally required to use any other register so probably wouldn't do so.
It's therefore highly unlikely that companies offering call prevention registers could realistically prevent you from receiving international calls.
There are several call blocking devices that you can buy which plug into your phone and help to screen and block your calls.
These range in levels of sophistication – and cost - including automatically blocking calls from a withheld number, only letting calls through to you from a friends and family list, and blocking a nuisance call from being repeated.
Some can also be managed via an online account. But it's worth noting that these devices can end up blocking calls that you do want. For example, calls routed via switchboards, such as those from your local hospital.