Apple, for some reason, didn’t included “send to group” feature in iOS, and you rely on selecting each contact manually to send a single text message. Luckily, we have an app in Cydia store which lets you send text message to groups.
With GroupSMS, you can send a text messages to a certain group created by you. Also, you get the option to send a text message to your entire contact list. GroupSMS is available in Cydia via ModMyi repo for $1.99.
Note: Normal SMS charges will apply while sending text messages via GroupSMS.