SMS services have so far been remained a huge source of income for US wireless carriers, but the high-margin SMS business has now started slowing down due to increase in the number of alternative services.

Users of SMS are paying in the range of around 20 cents a text to $20 per month for an unlimited text plan, generating a considerable amount of income for carriers.

But the increasing popularity of smartphones with access to messaging apps and email services is hitting the future of SMS very hard.

The number of texts sent during the second half of last year jumped 8.7 per cent from the previous half year to settle at 1 trillion texts, but it was the slimmest growth recorded in the past decade.

Services such as Research in Motion’s BlackBerry's Messenger instant chat service and Apple’s newly announced iMessage are expected to make surviving conditions more difficult for SMS.