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1-650-494-7081 (local tel)
email: DennisR@dair.com

How I fight phone spam

Overview

I wanted to block spam phone calls from reaching me on my mobile phone.
 

My phone setup

I use my own DairTel service within Telephone Message Pad to host my public 650-494-7081 and 855-DAIRTEL (324-7835) phone numbers. When either number is called, the call is forwarded to both my private office number and my private mobile phone number.

I have implemented adequate filtering on my public phone numbers so spam is not a problem. Calls made directly to my private numbers are a problem because I am forced to use less capable filtering.

Somehow, spammers have gotten my cell phone number and are placing automated calls to it directly. This is highly annoying. My anti-spam efforts consist of two parts: filtering incoming calls made directly to my mobile phone and stopping the further spread of my private mobile phone number.

 

Do Not Disturb

I looked at several alternatives (below) but ended up using a built in iPhone facility. The solution does not block incoming calls but, rather, prevents the phone from ringing at all. It is called "Do Not Disturb". You find it under Settings.

At right are the settings I use. I have it scheduled to run all day and so Do Not Disturb is always active. The setting labeled "Manual" is poorly labeled with a confusing description. A better labeling is "Enable". See discussion in following Activation section for my description.

I permit notification only from people in my contact list. There is some time and effort setting this up. Also, If you accept calls from people you do not know in advance, this method may not work for you.

 

Activation

In the Control Center, you will see a moon icon showing Do Not Disturb is Enabled or not. The moon icon and what I call the "Enable" above are merely alternate views of the same status. Because the moon appears in the Control Center, it may be easier to get to than going into settings.

If you have a schedule set, the documentation implies that the schedule is followed day after day. Changing the Enable (aka Manual), whether in settings or in Control Center applies only to today. I have not confirmed this is actually how it works. What is clear is that disabling either the Moon or Enable disables Do Not Disturb immediately. Given the schedule, enabling either the Moon or Enable enables Do Not Disturb and permits the schedule to be followed.

 

Allow texting

With the Do Not Disturb settings shown, all voice calls from your contacts will pass through. By default, Do Not Disturb active kills alerts from ALL text messages. So, in order to be alerted to new text messages, you need to identify exceptions.
 
Find a contact you want to receive text messages from. Click Edit and locate the Text Tone setting (see snippet at left). Click the caret and on the tone setting page enable Emergency Bypass (see snippet at right). You may have to scroll up to find the Emergency Bypass setting. Setting Emergency Bypass allows text messages from this contact to reach you. Continue for each contact you want to alert you.

Note that Do Not Disturb does not block any texts. You still receive all text messages. Do not Disturb merely stops the receipt of message from alerting you unless you set an exception.

 

Alternatives

Verizon offers blocking for its wireless customers but it had severe limitations for my case. You must identify no more than 5 specific phone numbers to block and renew the block ever 6 months.

There are apps which block calls for iPhone but require that the iPhone be jail broken.

There is a commercial service which blocks incoming phone calls, identifying which ones are spammers via crowd sourcing the black list. A disadvantage is the phone rings one time, exactly what I want to avoid.

 

Disable Caller ID

As noted, I do not give out my cell phone number so I imagine that companies are getting my number from caller ID on outbound calls I have made.

It turns out very easy to disable caller id from being sent on a call by call basis: prefix the phone number with *67. This code is what works for me in USA. The most common code outside USA is #31#. See https://en.wikipedia.org/wiki/Caller_ID#Disabling for codes used in your country.