Call-Em-All offers an unlimited conversations texting plan. This will allow you to use your text number to send text messages to individual contacts (or up to 15 contacts) as often as you need for the flat cost of $40 a month per number.
This is available to be used alongside your credits plan (it's available on our monthly plan for no additional cost).
Messengers will not be able to enable this feature, only the master account holder. You can enable this feature through the Conversations or Settings page of your account.
Through the Conversations page:
Through the Settings page: