Your DrayTEL IDs and passwords provide access to your account. If you disclose these details to anyone, or they manage to obtain them without your permission or knowledge, they would be able to log into your account and make calls, using up your call credit or running up call charges. This username/password combination must therefore be kept securely at all times - just as you would passwords for any other service (ebay, Amazon, Gmail etc.). You should always choose strong passwords for your account (both the account login password and your SIP ID passwords). Strong would be considered minimum 10 characters, mixed letters and numbers. If you are operating an IP PBX or some other VoIP proxy system, you should also make sure that that too uses strong passwords for its extensions, particularly if they can be accessed from outside your network.
Never leave default passwords on any accounts or hardware - change them to strong passwords. Also, ensure that you always use wireless encryption and beware using your DrayTEL account on networks where someone might be able to sniff your data.