Internet/Uverse is incredibly slow/spotty - already rebooted router + devices

We have AT&T everything, U-verse TV/Internet/Phone and a 4 device Mobile Share Plan. Our family has passed down our landline since we first got it in 1921.  

So we are a loyal AT&T cutsomer. But, recently, we have been experiencing major problems with our U-Verse service, mainly with our internet and phone. 

We're paying for the 18mbps service, but speedtests come out to about 3 mbps down and 0.2mbps up (with AT&T speedtest). Also, our internet and phone has been constantly dropping calls and connections. Its extremely frustrating. 

We have had this problem many many times before, and the customer service said it may be a line problem. Does anyone have any suggestions on the forums? 

Thank you.