If you are a permanent resident or citizen of Singapore you need to be at least 17 to order a landline. Otherwise you need to be at least 21 to get a landline. Mobile (cell) phones also have age restrictions on them, although these differ depending on the provider.
The main phone provider in Singapore is Singapore Telecom. They provide both land and mobile phones as well as Internet access. The telephone number for Singapore Telecom is 1-800-738-1311 or 1-609-738-1311. When getting a landline installed, it normally takes five business days. These phones are capable of both national and international calls. Check Singapore Telecom for applicable rates.
The three main mobile providers located in Singapore are M1, Starhub, and SingTel Mobile. Both pre-paid and contract plans are available, but an address is required for either. Rates vary depending on the company and what plan you choose. It is wise to do a little research before investing into a plan to see which plan is most cost-efficient for you based on the calls you think you might make.
Cell phones, landlines, and pay phones can all make international calls in Singapore. They all cost different amounts, and are usually more expensive then other methods including the internet and calling cards. Programs such as Skype make calling anywhere in the world cheap and easy.