USSD strings Returns "Unexpected Data Value"

[HOS]

Please help I'm struggling to get my Mobidata Edge USB modem to get a valid USSD response from MTN.
Using Hyperterminal I submit...
AT+CUSD=1,"*141#"

The response I get is...
+CUSD: 2,"Unexpected Data Value",15

+CUSD: 0,"This service is only available to Pay as You Go and MyChoice TopUp cus
tomers. Please dial *141*0# for other 141 services",0

This is using an MTN prepaid card which i have loaded with R10.00 from my phone just to make sure that the SIM card is OK.
I also ran the following commands to try to sort the unit.
ATQ1V1E1

And
AT+CSCS="IRA"

Please help getting really desperate.

 

[ginggs]

Using Hyperterminal I submit...
AT+CUSD=1,"*141#"

Try: AT+CUSD=1,"*141#",15

 

[HOS]

Thanks ginggs.
I'll give it a go again tonight (after-hours project).