Incoming Call not Connecting on Analog FXO Trunk

Hello,
First of all let me tell that I am an absolute novice at Telecommunications and IP telephony. So please forgive my ignorance.
To begin with, I have installed a UC 501 with 4 FXO and 1 FXS ports for my Home IPPBX project in India. So, far I have been able to configure:
1) 3 FXO Trunks from from different PSTN service providers.
2) 1 pjsip Extension(ID :601) through a Linksys PAP2 Analog phone adapter.
3) 1 FXS extension (ID: 201) through the FXS port of UC501.

I am able to call the extensions from each other.
I am also able to make outgoing calls to my mobile phone from both extensions. (Though this call is always connected through the first FXO trunk).

I have not configured any outgoing call routes so far ( yet I am able to make outgoing calls!! ).

I tried to configure an Incoming call route for my first FXO trunk, which should be ending on the FXS extension. Here's where I am stuck. When I try to call my First FXO trunk PSTN number from my mobile phone, after a few rings, the call gets connected but there's this message: "The number you are trying to call is not in service" and then the call disconnects.

I am not able to receive incoming calls on either of extensions.

Please help in the simplest terms possible.
Thanks in advance.

hi,

You can contact me on skype, i will help you to check it remotely. skype: chunlei.yi