After unlocking my Android phone "model QS5509A" go editions can't make call or send text

In Nigeria, I bought a new ATT phone/device which is locked due to go pay plan service policy. I Don't know the original buyer of this phone, but I was able to unlock the phone after requesting for unlock from att official site which was send to my phone within a minute. This means to me that the real owner must have pay all the bills. To my greatest surprise I unlock the phone using the code sent to me by att official site through my email account, I insert my country network Carrier e.g MTN NG, Airtel NG, Glo NG or Etisalat NG etc on the phone it shows the network Carrier name but the bar of the network bar is empty. This means I can't make calls or texts from the phone. Other activities like apps work fine on the phone. The only thing is that I don't have any means to make calls or send text just like saying the phone is useless as being a toy for kids to play games on it.

My questions is this, after unlocking the phone or device using your unlock code sent to me through my email:

1.WilI I still wait for 6 month to get the network bar show up on it so I can make calls or send text messages? 

2. Does it mean is not fully unlock to other network Carrier or depending?

3. Why should I exprience such act after unlocking the phone with your unlock code? Etc.

Please I need urgently required answer to my request thank you.