DSL Internet keeps disconnecting every half an hour

I just cancel my AT&T 1Gbps fiber optic internet circuit, for $80, which is a $10 discount off of the normal monthly rate.  I have had it for 6 months and I use less than 10% of that circuit speed.  It has been terrible on and off the whole period.  Originally when I had it installed, I was happy to see the fast speed test and felt good about it.  A few days into it, I noticed that many times my devices were getting connections rejected (authentication errors).  In many instances, I had to rely on my old internet connection, because the AT&T circuit was so unstable.  I made a few calls in to their support but little was done to stabilize the connection issues.  I had hoped that it would improve, but it never did.  At times when we thought we were using data at home wifi, our cell phones were eating up my cell phone data plan, because the att circuit connection was in and out.  To make matters worse, I am now being told that I have to pay a cancelling penalty of $180 ($105 + 26 days of credit remaining in month already paid for).  I voiced my severe disappointment in the service, and ETF (early termination fee) for something that was performing less that half (50% down) the time.  The ATT rep said that I could have cancelled in the first 30 days and there would not be a penalty.  Now I wish I never did give them a shot or should have cancelled within the 30 days.   ATT has fallen away, from what it used to be, with regard to internet service.  I would not recommend ATT for home or certainly would not consider recommending ATT for my organization.  They have alot of technical issues they need to iron out before they sell their internet service.  I am done!!