yahoo web hosting server and slow ftp upload

I am using a mac running system 10.8.5 and trying to upload files to yahoo's web hosting server via ftp. The upload is extremely slow. I've contacted them several times and they say there is nothing wrong at their end. Although yesterday they admitted to seeing the slow speed and by the end of the call said there was nothing wrong at their end???

I had cable check the line, it is fine. We did a test and I can upload to youtube very quickly. I also tried uploading to the same yahoo server on a different computer to rule out a computer problem, the upload was equally as slow. As an example it took 12 hours to upload a 600mb file. It also took over 2 minutes to upload a 2.2 mb file. I was using Transmit. Then yahoo suggested Filezilla. Which I also used. Both uploads were the same. Also after my file did finally make it over, I had an error message in Transmit that said -132 could not send file to remote host….even though the file copied across. Another time I got a -135 socket write error.

I'm not sure what to do. It's not the cable connection, it's not the computer, it seems to be a problem between the ftp software and yahoo's server. Has anyone else had this experience with really slow uploads to yahoo's web hosting servers and what was the solution?