I would like to know what "upgrading" fees are? The guy who's mining my account says I need to pay him $1005.50 more in Bitcoin before they can go on. I only invested $300.00. Does it sound correct?
You are being scammed.
Individual accounts do not need mining, mining is required to secure the network as a whole.
This is a common scam, where they ask you to "invest" a certain amount into mining, and then string you along by asking you to pay more to unlock better returns, or unlock your keys, or whatever other nonsense they can come up with.
Cut your losses and write of the $300, do not send them any more funds.