SMS sending limit was introduced not later than Gingerbread. As far as I know, and I investigated thoroughly, limits vary from API to API, and it is generally impossible to override these limits on non-rooted devices. If possible, those are rare exceptions. I think current minimum is 30 messages in 30 minutes, but this is subject to change. Google is the boss.
That being said, if your app is supposed to send messages from your device only or from controlled number of devices, you may get around this problem by rooting devices and then setting SMS_OUTGOING_CHECK_MAX_COUNT to a huge number (say 99999) in:
- /data/data/com.android.providers.settings/databases/settings.db
- table secure
- table system
- /data/data/com.google.android.gsf/databases/gservices.db
- table main
Also, if you're developing an app for a single API, you should Google its specific limit.