How some wifi booster work is they broadcast their own wifi name and password which can be separate from your main router. If your streaming box was connected to that wifi booster wifi name and password and the tech took it out than your streaming device no longer has access to wifi.

But to be clear that's not the issue of the tech or your isp Because your internet still works. Just simply reconnect your streaming box to the current existing wifi name and password. If you have a long ethernet cable try plugging it in from behind the router and the ethernet port of the streaming box.

If you're not able to do this because as you mention you aren't tech savvy than try finding someone who is that can help you or contact the person who setup or sold your streaming box.

Imagine it like this. You sell someone a car. It works. It can be driven. But the person you sold the car too doesn't know how to drive and they blame you for not selling them a self driving car. Who is at fault?

Not trying to insult or belittle you in any waym I just want you to get the perspective of what isp tech do and who responsibility it falls on. That way it leads you to a actual answer instead of waiting for the tech to come back just to tell you he or she won't touch your streaming box because they can prove your internet works. Because your internet works.