First I'd like to tell you the troubles I had to deal with when I purchased the server. I was given a Cs:s by mistake, I have to say, few minutes after I submitted the ticket they helped me and it was all good. After that only 4 people could connect by ip, which was a pain because I like to scrim and I need at least 8 people in the server to be able to play. Again they dealt nicely with the problem and I was happy within an hour of sending the ticket. Now 8 slots are not enough for me, because I like to have people spectating our games, so I submitted another ticket, this time I asked them to change the l4d_maxplayers cvar to 16, and I was told that I needed to purchase 8 more slots, and that's what I did, but now nobody can join the server, it gives a "server is full" error even though its completely empty(0/16). I send a ticket about 6 hours ago and the only answer I've gotten is "Have you tried restarting the server from the Info panel? Sometimes that clears it up.
What mods are you running on the server?"
I immediately answered. I just want to play on my server, it's been around 6 hours since I answered.
I really feel like I've been scammed because I've bought many servers in my years of gaming(from other companies) and I haven't had any issues with them.

I'd jump onto the IRC and see if you can get an answer, even though there might not be too many people on at the moment. Just go to gamesurge.net/chat and then /join #gameservers

Is it still possible to have your server replaced if in case you mistakenly purchased a server for the game that you won't going to use?

Yes, they will be able to swap the server to a different gameserver for you