Hi,
That's almost certainly not correct, no. Your Internet provider is extremely unlikely to have the whole of 46./8 allocated to them. That'd be over sixteen million usable IPs, and a fairly large chunk of the Internet. In all likelihood the network range is 46.126.40/24, but it could be anything smaller or a bit larger than that.
My advice in understanding this whole thing would be: forget about all this Class A, B, C stuff. The important thing is the netmask. In day-to-day life you'll seldom encounter any external Internet-live IP ranges that are larger than a /24. In private network ranges it's not unusual for /8 or /16 to be seen, certainly.
I think at this point it would also be helpful to explain what it is you're trying to do, and why you think you need a huge chunk of the 46/8 part of the Internet to do it.
Edited to add: also, there's no way you or anyone anywhere can buy a whole Class A ! The IPv4 address space is almost entirely exhausted worldwide at this point. What almost everyone on domestic or small office broadband does is use an internal private network range, like 10.x.x.x or 192.168.x.x, and then use NAT to talk to the outside world on a single IP or far smaller number of live IPs.