San Francisco-based Twitter said Wednesday evening that the firm has stopped delivering SMS over the firm's UK number, along with other countries. According to Twitter, the firm said that the move came because of the expense of delivering SMS messages to people, saying that the cost of sending message to followers via SMS had become too expensive. Twitter explained that even at a limit of 250 messages received per week, it could cost the firm about $1,000 per user, per year to send SMS out of Canada, India, or the US. The company said it was hoping to establish "fair billing arrangements" with the mobile operators in other countries rather than pass on the cost to its users. According to Twitter, it will continue to offer SMS support in Canada, India, and the United States, and is working on introducing new, local SMS numbers in countries throughout Europe, along with continuing negotiations with carriers in other countries.