API (via getting [400] Invalid phone number format - but I'm not updating the phone number!

  • 21 August 2023
  • 2 replies


Hi, i wonder if anyone can lend me some assistance (I’ve messaged support also)

I am new to Klaviyo - migrating from mailchimp and so far so good!

However I am running into an issue trying to update a single profile property across all my contacts via a module.  (API)

I created a scenario which successfully updated 377 profiles correctly with my desired property taken from my CRM database (Airtable)

However, all of a sudden I started getting the error: [400] Invalid phone number format (Example of a valid format: +12345678901)

I am NOT trying to update the phone number and this field has been left blank (which as i said worked for the first 377 times!) 

I have also tried putting my own phone number (in the correct e.164 format) and still get the error.

I tried putting “null” in the phone number field and this also throws the error.


I saw a post about needing to set up SMS in Klaviyo settings (which i don’t want or need!) so I have gone through all the steps I am able to do this and my UK region is now “active”. I’m not sure if I’ve missed anything but this hasn’t helped either!

A slight issue is that when I create my region (UK) - an “Australia” entry always pops up - if i delete it, it removes my UK entry too! It now seems that I must complete a registration form to send SMS in Australia, despite not living there, having an Australian business licence or even wanting to send SMS messages at all! 

It seems from other posts that this phone number requirement has been glitchy in the past, but can anyone tell me if it is possible to use Klaviyo if I do not need or want to send SMS messages? As this would really be a deal breaker at this stage!


Many thanks in advance for any insights you might have…



Best answer by bikemandan 21 August 2023, 13:57

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2 replies


I have now resolved my own issue.

I realised that the records that were being returned we always the same. There were a group of “profiles” that all had my email address (from historic tests) and may have contained a phone number (although couldn’t see one).

Somehow, filtering these records out from going to the update module has allowed it to work again - a little strange and I’m still not sure WHY it’s happened as the update module was not touching the phone_number field at all, but am relieved I can at least press on for now! 

I’m sure I’ll be back as my ideas get more complicated!

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Hello @bikemandan,

Thanks for sharing coming back and sharing your findings on this odd behavior! 

Glad you’re able to continue with the work you’re doing after some investigating.

Thanks for being a part of the Klaviyo Community!