Overselling, what is it?
Overselling is when a company chooses to sell more resources than they actually have. For example:

A companies server has 250gb of diskspace and is given 2tb of data transfer.
They offer 100gb space and 1000gb(roughly 1tb) of data transfer, for only $8.

That is what we call, overselling.

How can we stop it?
Unfortunately, we can't. To many big hosts have to many customers which like the overselling part of webhosting. Your best bet is to go with a host that doesn't oversell, such as Velaxi. Overselling always has been a big bump in the market, especially when you've got the big hosts that can afford to spend $1mil just to get it popular.

Prove that you don't oversell!
We don't oversell, all of our packages, the space and data transfer, are dedicated to the desired package you own/want. By us not overselling, we're able to keep our servers in a nice and fast condition, rather than loading it up with customers.

So why don't you buy a shared hosting package, seeing as we don't oversell?