connection problem or invalid mmi code

[SaadPatel]

Hi guys.
Whenever I dial a phone number or a service code and press the dial button, im getting an error -"connection problem or invalid mmi code " and the dial fails. The network strength remains full. This happens occasionally and I do not receive calls or any communication from the network.
In short, I lose connection with the network somehow. I changed my sim card to see if that solves the problem but I had the same problem with my new sim. So obviously this must be a device related issue. Pls help coz its very frustrating to not being able to perform basic functions using the device. Pls advice me asap.

[Uliwooly]

Have you contacted your carrier/network regarding this issue? 

[SaadPatel]

As I said, I had changed me sim. The new sim was of a different carrier. Had the same problem. So most probably it isnt a network problem, right?
Also, I tried factory reset..worked like a charm for a day but started having the same problem the very next day!
Help help help!

[Uliwooly]

It could be an app acting up, do a factory reset and do NOT install any app, test it for a day and see if you get the same issue, if you don't then its an app 

[Niranjan_NM]

I have been facing same problem since 2 months with my xperia t2 ultra dual, still i am not got the solution....!!