To block a phone number, send a text message to 9999 containing the word block and number you want to block:
Reply from 9999: SprintFreeMsg: Text messages to and from "1234567890" are now blocked.
It works with short codes too.
block 1234 - Reply from 9999: SprintFreeMsg: Text messages to and from "1234" are now blocked.
And with email addresses:
block firstname.lastname@example.org - Reply from 9999: SprintFreeMsg: Text messages to and from "email@example.com" are now blocked.
You can even block an entire email domain:
block @spamco.com - Reply from 9999: SprintFreeMsg: Text messages to and from "@spamco.com" are now blocked.
Or all texts from all email addresses:
To see what's blocked use the list command:
list - Reply from 9999: SprintFreeMsg: There are 3 senders in your block list. These senders will be blocked "1234567890", "1234", "firstname.lastname@example.org"
To unblock a sender use the allow command:
allow 1234567890 - SprintFreeMsg: Text messages to and from "1234567890" are now allowed.
Allow also works with short codes, email addresses and email domains. Use allow email to unblock messages from all email addresses.
For help with the 9999 service send the help command to 9999:
help - Reply from 9999: SprintFreeMsg: Text these commands to 9999 to manage SMS blocking: block, list, spam, help. Text “help <command>” to learn about each command.
There are more commands but the others are mostly synonyms for the ones listed above. Sprintusers.com has the complete list in PDF format.
The 9999 text message blocking code only works on the Sprint CDMA network. It doesn't work with Boost or Nextel iDEN accounts or with AT&T, Verizon or T-Mobile. An alternative is the SPAM (7726) short code which works on all US networks. Forward a text to 7726 to report it as SPAM. But 7726 doesn't actually block the numbers you report. It also may not be free, I was charged when I used 7726 on Boost but not on PlatinumTel, Page Plus or T-Mobile prepaid.
If you try 9999 on Virgin Mobile or any Sprint MVNO please leave a comment letting us know if it works.
Unfortunately 9999 only blocks text messages, not phone calls. If anyone knows of a way to truly block unwanted callers on any network, I'd love to hear about it.