complete downloads instead of repeated timeouts

On data cap I have repeated stalls - then quits!
This uses Precious data - and my time baby-sitting to make sure it completes.
Just now a download got up to 100% - waited a few moments and QUIT! So I had to restart it.
This is Really Frus-Tra-TinG ! !! !!!
I now have it set on slowest possible setting but that Still Did Not Help!
Can you do ANYthinG to FiX this? Please!!

Have a very Fine pleasant day!!!!!!!!!