Unable to dial out ...

Hi I recently experience this problem that I was unable to call out from my phone,SMS and call receiving work fine
I update to 3.1.2 last night but didn't work until I take my phone to one of the mobile retailer store today and it back to normal again,the technician said he did not do anything

this problem happened twice- the phone suddenly unable to call out and it back to usual randomly
the 1st time took 1hr to recover and 2nd time took more than 12hrs

this is really fustrating and I don't know if it's going to happen again next time
anyone got any idea how to solve this permanently ?
Thanks

---

Orignal From: Unable to dial out ...