[Speed] Slow sustained uploads. Tech coming and don't want to be charged

Hey all I backup my computer to the cloud and have been doing so for months. I'm on the Blast package (50/10) and have been able to backup at around 9~12 Mbps for months on end. About a week or so ago, I notice that when backing up a file, it was taking way longer than it normally does. I thought my backup provider was having temporary network issues so I let it slide. After a week or so of this behaviour, I got fed up and was about to open a support ticket with them but decided to check my uploads to to other places. I tested uploading to Amazon Cloud, Dropbox, and Comcast's own email servers and they all gave me the same speeds as my backup provider....a couple of Mbps at best. When I run a speed tests, everything looks fine but it's the sustained uploads that are an issue. I called Comcast tech support and they ran a test on the line and she told me that she saw something that wasn't normal and that they would send a tech out. I asked if I would be charged for the tech visit and she said maybe depending on what was causing it. She couldn't go into specifics about what she saw. Only that the tests showed a problem. I have done the following to make as sure as possible it's not something on my end... 1. I've reset my modem to factory defaults. 2. I told the Comcast automated line to send a reset, or whatever it's called, to my modem. 3. I've tried different coax cables to 2 separate jacks in the house. 4. I've tested it on another PC. 5. Tried different network cables. Non of the above changed anything. I've seen the videos on YouTube and I'm concerned they are going to come out here and find some excuse to charge me. I'm looking for suggestions on how to handle this. I do not want to get charged! Is there anything I should look for in the router? Single levels and such. I'm kinda clueless about many of the things it shows in there but if you tell me what to look for, I can probably find it. Are there any further questions I should ask before the tech visits? Any questions I should ask the tech? Anything else that I could check? How do I speak to someone in tech that will give me a bit more info on exactly what it is they see wrong with my line? So on and so on. Thanks Here's my specs and info: City: Miami, FL Modem: Netgear C3700-100NAS. 3 months old. Firmware: v1.01.11 Wifi: Turned off Antivirus: None Firewall: Just the standard Windows firewall. Operating systems: Windows 7 64 bit and Windows XP Thanks