Level 1: Cadet

SMS error code 21

I've never experienced this problem whilst sending my friends an SMS or a call, I have service, bought a new phone as a solution which didn't work and I know for a fact that my number hasn't been blocked. Please help.

Was this helpful?

  • Yes it was, thank you
  • No, I still need help
Level 25: The Singularity
Level 25: The Singularity

Re: SMS error code 21

An error code 21 on an SMS is usually because the number is entered wrong in the contacts list. It may be entered in internatioanl format and have the zero included (eg +61 0427 XXX XXX) when it should be without the zero (eg +61 427 XXX XXX).


Have you tried entering the number in directly when you are trying to send the sms?

Never be afraid to back yourself when trying new things, just always make sure you have 3 escape routes if things go wrong.

Telstra 24x7®

Take care of your Telstra services in one place with the Telstra 24x7® App for Android

Find out more
Find out more about the Telstra 24x7 App ×
Manage your services and take advantage of offers while you’re out and about with the Telstra 24x7® App Find out more
Earn points on our new rewards program and enjoy tier benefits like discounted movie tickets and moreFind out more

Need a hand or want to share your expertise?
Register for CrowdSupport and get involved

Register now