Unfortunately, we have no idea what the technician might have done, and it is difficult to know what particular settings your provider's service might require.....or even whether the AirPort Extreme is fully compatible with a new connection or type of service.....especially if it might be a fibre type connection. (The AirPort Extreme was designed to work with normal DSL and cable type connections.)
Your best bet is to get the technician back out at a time when you can check the connections to make sure that everything is working before the tech leaves.
We can give you a few connection settings to check......assuming that you can access the settings for the AirPort Extreme using AirPort Utility. But, we would be reluctant to tell you to change any of the settings at this point......since the connection settings are interactive on the AirPort Extreme. Change one thing....and another setting will change somewhere else.
If you open up AirPort Utility on your Mac (Finder > Applications > Utilities > AirPort Utility) and click directly on the picture of the AirPort Extreme, does a smaller window appear with an Edit button?
If yes, click the Edit button and the next window will appear with tabs at the top of the window for Base Station, Internet, Wireless, Network, and Disks.
Post back on your results.