Hi The phone company told me I have an "open faulty line" but told me I would never be able to understand if they tried to explain!! Anyway, does anyone know what this is and what causes this problem.. Thank you

Your Phone completes a loop when you lift the receiver, with 2 wire from the phone company(red and green usually for single line(or White/Blue, and Blue/White for Category Rated wire)
I think it is possible the tech? You spoke to took a long time understanding that concept, and figuered it would be difficult for someone to understand.
If you call your phone from some where else, does it ring and ring(open line)? Like what telco says or busy(shorted)?

If your phone doesn't work outside where phone comes in, the line is open(broke) between the box and their company, and is their responsibility.
If your phone works outside and not inside it is Your wiring, try different phones, jacks or line cord.