The first thing you need to do is identify the company that you are contracted to, particularly if the problem is covered by a warranty.

If you've bought both the handset and connection to a mobile phone network from a network service provider you will need to see that provider about problems with either the handset or the service connection.

If you have bought a package from a retailer, problems with the handset may need to be directed to the retailer while problems with the service to the mobile network should be directed to the network service provider.

Check your paperwork, it should be explained there. If you have billing problems you should contact the number supplied on the bill.

In all cases the first step is to contact the retailer or network service provider to try and sort out the problem. Be calm but assertive and have any documentation such as the network service connection agreement, receipt or bill handy.

If you have no luck, ask to speak to a supervisor or manager. As a last resort, you can contact the Telecommunications Industry Ombudsman (toll free 1800 062 058) for problems with a network service provider. If you have problems with a retailer over a handset you can contact Consumer Affairs (toll free 1800 019 319).