good alternative to iMessage?

Are there good alternative to iMessages? Just switched to iPhone after 10 years of Android, and we love it! But it has a huge problem; iMessage must have a data or wifi connection to send texts. Our area is filled with pockets without good cell service and this really handicaps texting (which we rely on heavily because of school and activites). Hoping to find an alternative otherwise we'll need to go back to android.