Hmm, this is going to be very hard to explain. What you're needing is a full Coral admin course. If you got one of of these you'd be able to do all the MACs (Moves, Adds, Changes) yourself to save yourself the PBX tech fees.
Let's start with the basics.
1. What type Coral do you have - FlexiCom 200/300/400/5000/6000, IPx 500/800/3000/4000? Each will look different and have a processor which, depending on system and age, will have a different name. The processor will be MCP/MEX/MEX-IP/MEX-IP2 etc. The processor will have a DB9/25 port on it which is labelles KB0 and is used for programming with a null modem cable.
2. I believe posts with passwords are removed on this forum so I can't post it here. It's likely the default has been changed anyway. Login with this once you know it.
3. Look at the FAQ for basic commands and explanation of how the menu works.
It's pretty self explanatory - I taught myself many years ago. It's all in English and laid out logically.
4. As per the FAQ, all commands are access via simple words eg HUNT for hunt groups, NPL for numbering plan, NET for networking. You'll need to start at NPL and use the 1 option to display all. Depending on size of system this may large so you may want to capture to file. Work out what your local and remote xtn numbers are - KEYSET, SLT, NETWORK, PUB_LIB etc
5. Use PLIS to display details on the xtns when you know them. This will display info such as shelf/slot/circuit for physical xtns (if it's IP then that's a whole other kettle of fish

). Also look for the details on the NETWORK number like it's NODE.
7. Then once you have all those details, go back to NPL and DELETE (do NOT use ERASE or you'll be up the proverbial paddle

) Then use ADD to add the numbers back in but in the oppostite place from where you deleted them from - for this you will need the shelf/slot/circuit or node information you got before.
Make sense? That's it in short form. Obviously sitting on a proper Coral admin course would be extremely beneficial if you're going to be doing a lot of it. If you're not technical, or at least telephony savvy, then it will take a long time to pick it up.
Hope that helps. Post if you need more help.