AT&T Inc is following bigger rival Verizon Wireless with a new type of family plan that comes with a four-fold increase in its fees for data services such as mobile Internet. But, unlike its rival, AT&T says the plan will be an option rather than a requirement for new customers and subscribers upgrading to a new phone. Late in August, AT&T, the No. 2 U.S. mobile provider, will launch the new offering, which allows its customers to buy a single data plan for up to 10 devices and includes unlimited phone calls and text messages. Under the plan, the company's data price could be quadruple its current fee. For example it will charge $40 for 1 gigabyte of data per month, compared with its current rate of $30 for 3 gigabytes. The hope is that the new plan, similar to one kicked off by Verizon Wireless in June, will entice individuals and families to connect more devices such as tablet computers to the AT&T network because they will no longer have to buy a separate monthly data allowance for each mobile device.