Adding a phone number to your Google account can make it less secure

Sure I can see problems with that. My initial feeling is people will thing that such support is a scam, but that at least shifts the position of Google from "we can do such support" to "we don't want people bad mouthing us so we're going to refuse to do that support even if it were prima facie profitable".

I don't doubt that a telecom would do such a thing as you describe but have some hope that you're just not seeing the back end confirmation?

The issue is that they don't discriminate between carriers that perform good identity checking and those that don't.

(Reliability is actually well-addressed by Google - they offer this as a supplement to the other forms of verification they provide.)

Background: I have worked in IT Security at an Australian bank, and had close ties to the Internet Fraud department to help them understand fraudster's tactics.

Many banks use SMS for 2FA. Australia has a law regarding how long it should take customers to switching telco providers (called 'Porting' because your retain your phone number), and the timeframe in which this must be completed (90% within 3 hours, 99% within 2 business days). If the Telco doesn't complete in this time period, you can raise a complaint to the Telecommunications Industry Ombudsman.

Example: If you are currently with Telco A, to port your number to another company, you call Telco B and provide your details. They take care of the porting process, and you can have your service running on a new phone and SIM within 3 hours.

"All you need to have with you is your mobile number, the name of your old mobile provider, your account type (pre- or post-paid) and your account number. We'll handle the porting process from there. It can take from three hours to three days, but we try to do it as fast as we can." Source: https://www.cnet.com/au/news/switching-telcos-easier-than-yo..., 2012

To make matters worse, the fraudsters would then change the details at the new Telco B (i.e. my address is now 123 Rainbow Road, and my mother's maiden name is Smith, not Jones). When the victim called Telco B, when Telco A told them a porting request had been completed, they'd say "Sorry, we have no idea who you are and the details you're providing don't match our records". It can take days to sort the whole thing out, by which time, your Internet Banking has been compromised and funds transferred out.

This was a major problem for Australian banks, because they cover the losses for customers if you lose funds as a result of Internet Banking, as long as you weren't negligent (e.g. you left your Internet Banking logged in on a public computer in a library, or something).

If you are relying on your telephone number as a security mechanism, I would change to something else. Something you have, ideally (Google Authenticator, a physical hard token, etc.).

Sources: ACMA Porting Rules for Telcos: http://www.acma.gov.au/Industry/Telco/Numbering/Portability/... Example A: http://lifestrategies.net.au/wp-content/uploads/2015/03/Marc... Example B: http://www.itnews.com.au/news/45k-stolen-in-phone-porting-sc... Example C: http://www.news.com.au/finance/business/banking/customer-sca...