Thousands of mobile phone users were left unable to use their phones following a blunder by the BBC's consumer advice programme Watchdog. Many who tuned in were disturbed by a security flaw which lets phone thieves swop SIM cards to other handsets but continue to use the victim's account to make calls. Host Anne Robinson explained how criminals then run up bills costing thousands of pounds by making lengthy calls to premium lines which they have stakes in. Scroll down for video . Watchdog presenter Anne Robinson,  explained how mobile phone users can protect their handsets from thieves, but failed to relay an important detail, which locked thousands of irate people out of their handsets . But when viewers followed on-screen steps telling them how to protect their SIM card with a new code, they found it made their phone unusable. The BBC had omitted a very important detail – you need the network provider's default code to change the security SIM code – as without it the mobile becomes automatically locked. Viewers turned to Twitter to vent their fury in a stream of tweets, criticising the BBC for giving erroneous advice, which it only corrected 15 hours later. Callers to the key network provider EE jammed its switchboard as they desperately tried to get their phones working again. Sarah McCormick tweeted: 'I was trying to set up a SIM pin and locked my SIM – need a PUK code but can't call to get one as I don't have a phone!' And Sarah Parmenter, from Southend-on-Sea, tweeted: 'I think the whole country is trying to get PUK codes right now. That wasn't clear whatsoever in the programme. Grr!' A BBC spokesperson said: 'BBC Watchdog did not give out instructions on how to set up a PIN for SIM cards, nor did we give out any on-screen steps that viewers should follow. 'Whilst we did advise people to get a security PIN to protect themselves against fraud, we told them to check their phone's instructions before attempting to do so.' The BBC failed to advice users that they needed their network provider's default code to change the security SIM code - without which - the mobile phone is automatically locked, prompting outrage on Twitter .
Anne Robinson told how thieves can run up bills on stolen mobile phones .
Watchdog gave instructions how users can protect their SIM cards .
The BBC failed to pass on a vital information on a network security code .
As a result, thousands of users discovered that their mobiles were locked .
Outraged viewers took to Twitter to express their anger over the blunder .
Thousands of mobile phone users were left unable to use their phones following a blunder by the BBC's consumer advice programme Watchdog. Many who tuned in were disturbed by a security flaw which lets phone thieves swop SIM cards to other handsets but continue to use the victim's account to make calls. Host Anne Robinson explained how criminals then run up bills costing thousands of pounds by making lengthy calls to premium lines which they have stakes in. Scroll down for video . Watchdog presenter Anne Robinson,  explained how mobile phone users can protect their handsets from thieves, but failed to relay an important detail, which locked thousands of irate people out of their handsets . But when viewers followed on-screen steps telling them how to protect their SIM card with a new code, they found it made their phone unusable. The BBC had omitted a very important detail – you need the network provider's default code to change the security SIM code – as without it the mobile becomes automatically locked. Viewers turned to Twitter to vent their fury in a stream of tweets, criticising the BBC for giving erroneous advice, which it only corrected 15 hours later. Callers to the key network provider EE jammed its switchboard as they desperately tried to get their phones working again. Sarah McCormick tweeted: 'I was trying to set up a SIM pin and locked my SIM – need a PUK code but can't call to get one as I don't have a phone!' And Sarah Parmenter, from Southend-on-Sea, tweeted: 'I think the whole country is trying to get PUK codes right now. That wasn't clear whatsoever in the programme. Grr!' A BBC spokesperson said: 'BBC Watchdog did not give out instructions on how to set up a PIN for SIM cards, nor did we give out any on-screen steps that viewers should follow. 'Whilst we did advise people to get a security PIN to protect themselves against fraud, we told them to check their phone's instructions before attempting to do so.' The BBC failed to advice users that they needed their network provider's default code to change the security SIM code - without which - the mobile phone is automatically locked, prompting outrage on Twitter .
criminals then run up bills costing thousands of . Watchdog presenter Anne Robinson,  explained how mobile phone users can protect their handsets provider's default code to change the security automatically locked. Viewers turned to Twitter on how to set up a PIN for SIM cards, nor did we we told them to check their phone's instructions before attempting to do so.' The BBC failed to advice users that they needed their network