I don’t use pastebin, but I can’t imagine a scenario where you shouldn’t be able to delete the files once there. Since it’s on the Sangoma pastebin instance, you could try sending in an Issues request (top of the screen) and ask one of the Sangoma pros to handle it.
Rather than worry about “if” someone is scanning your network (because they just are), set up your Integrated Firewall and exclude everyone that tries. Also, for safety, go into the Advanced Settings tab and make sure that “Anonymous” access is disabled. After that, make sure that port 5060 on your firewall is only open to people you want to have access.
For access to other services (none of which should be exposed to the Interwebs), make sure the Firewall router blocks everything incoming, and make sure the Integrated Firewall (in FreePBX) is set up so that nothing is in the Internet Zone. The Wiki has information on securing your network using FreePBX. Here are a couple of threads where we’ve talked about port security.