|There are actually, a number of things to consider.|
First and foremost....where bandwidth is concerned it is important to note that you'll never get more than about 80% of your rated bandwidth. Which is to say, if you have a 10 Mbps connection to the internet, on your best download you won't exceed about 8 Mbps. The reason being, a certain amount of bandwidth is taken up by overhead.
I won't go into a long discussion about this because if you're not a network geek like I am, it won't make any sense. Just accept that this is true in all cases of TCP/IP networking on a contention based network.
What DanJ said above is very true. I'll add to that.
If the segment of the ISP's network you're on is really busy, then that will affect your bandwidth. If you share a segment with a lot of people running P-to-P software who share files 24/7, or, a bunch of them are all downloading big files all at the same time, that will eat up bandwidth too and cause lag/latency issues. If it's a peak time of day for internet usage, this will also cause issues.
What I don't understand, until the upgrade, I was receiving 5 MB without any problem. This problem only started with the upgrade to 10. So once again is the problem my modem, or the provider's service?
This is indicative of something that isn't caused by you. This is more likely something on the providers end. However, the person you're talking to on the support line is likely not much of a technician and just reading from a Q and A database. If your question isn't in the database, you don't get a reply. What you need to do is call your ISP's support line and ask to talk to their 2nd level support. This should be the guys (and/or gals) who actually do have a clue and are able to fix things. Talk to them, explain whats going on and how it just started since you upgraded to a higher bandwidth package. There just might be something they can do to reduce your latency and improve your connection rate.