Sources suggest that the Verizon SMS Cause Code 98 error means "destination not authorized to receive".
Here are some steps you can try to follow and get the issue resolved:
Confirm that the destination number is 10 digits in lengths.
Verify how much device memory is available on the phone.
Check to see if there is a software update available on the device.
Delete any long threaded text conversations.
Perform a battery and sim card pull (if it’s a 4G device) on the phone.
Once you have completed these steps, please retest the SMS service for consistency. If the issue still persists, contact Verizon Customer Service on (800) 922-0204 or dial *611 from your mobile phone.