Incoming texts are showing up as coming from the incorrect phone number - last 3 digits are matching incorrectly

ervinasFM

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Hi everyone,

We're currently experiencing an issue where incoming texts to 3cx are showing up as coming from the wrong phone number. If for example, we send an outgoing text to a number who's last three digits are 311, when they respond it comes in as if it's from a completely different contact/phone number which happens to share the last three digits as the correct phone number/contact.

We use Twilio for our trunking and have had zero issues with how they are formatting and sharing information with the 3cx system which is how we know it's not on their end. The only way for us to verify who is actually texting us is actually to check the Twilio logs which always correctly show who actually sent the text, despite 3cx saying it's coming from a different contact/phone number.

We are struggling to resolve this issue as it seems to be possible the short codes are getting mismatched in 3cx, does anyone have any possible solutions or advice? Is it an issue on the backend with how short codes are being identified and associated with phone numbers in our system? Is this something we can adjust or has anyone had this issue? As we're growing our business it's becoming a much larger issue everyday as more phone numbers are put in 3cx and many will inevitably share the last 3 digits.

For reference we do have everything configured correctly for E164 format as this is required on Twilios end and must match formatting in 3cx as well.
 
Can you advice on your contact matching setup?
 
I discovered today that I'm having this exact issue. It doesn't have to be a contact, it's just someone who previously texted in.

This happened with a customer on 12/09/25 and I thought it was an anomaly. It happened with another customer today 12/13/25 and I lost a job because of it.

I'm on V20.0 Update 7 Build 1080. I'm using VoxTelesys for my SIP trunking provider.

No CRM integration or anything like that. This is all within the 3CX web/mobile app.
 
Okay, I dug into the problem a bit.

The issue lies with Caller ID Matching being enabled and set to 3 digits.

Admin > Voice & Chat > (Trunk Name) > SMS

There's a check box for Enable Caller ID Number Matching. It's default is 3 digits. Depending on your use case and circumstances, this should be either 10 digits (In the US) or disabled. Not sure why I enabled it in the first place, or if it was a default..

Anyhow, what this is for is when your inbound caller ID doesn't always match the number formatting (E.164) from your SMS provider. Then you might end up with SMS threads that aren't associated with the contact in the 3CX phone book.

In my case, I've disabled this, as everything with my SIP trunk provider comes in as E.164. Hopefully, soon, an affected customer will text and I'll know if I fixed it or not.

Why didn't this cause an issue for me before this? Luck of the draw, most likely.

I'm probably "different" in that I tend to keep SMS threads forever. I'm a small business and it works better for me that way. If I purged chat logs every three months I probably would never have noticed the problem.

Anyhow, hope this helps.
 

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