You can do this in many different ways. Either use translation pattern in the inbound CSS as you do or transformation pattern to change the called number by using the transformation CSS option. But the simplest way is to just use the prefix DN in the inbound call section on the gateway to simplify add 777 in front of whatever you get from the gateway.
Apart from this there are other options, but let’s stick with these for the time being.
What you should know is that you can never mix traditional call routing, like TP, RP or DN, with transformation patterns as that would have severe impact on your calls.
Apart from what I previously wrote this article is a great read if you want to understand the use of transformation patterns in CM. Understanding the 5 uses of Calling Party Transformation Pattern in UCM It's written by the great Vik Malhi, likely the most gifted trainer that I ever had the pleasure of having attending a class with.
Hard to say if it could have been the settings you mentioned that your colleague had touched as your not sharing what it was.
Two things, originally you wrote this.
”Dialed number : 4551218
Number needs to translate to 7774551218”
In your screenshot of the TP it shows that you translate to 7774351218, that is not matching what you originally wrote.
Secondly does the outbound CSS used on the TP see the PT where you have your directory numbers?
Based on the name I would guess that this CSS would be used for egress calls that has international call privileges. If so that would likely not be the appropriate CSS to use for the outbound CSS on the TP.
It is directly inappropriate to have inbound calls sent to a CSS that sees partitions used for egress calls as that opens up for call loops. Strongly recommend you to change this. Inbound calls from external parties only need to have visibility of partition(s) that holds directory numbers.
