I often hear mistakes with these three verbs.

Problem:
These verbs are spelled similarly but have different meanings.

Explanation:
The verb “assure” — spelled A-S-S-U-R-E — means to state with confidence to, as in “I assure you that the ambulance will arrive within seven minutes.”

The verb “ensure” — spelled E-N-S-U-R-E — means to guarantee or secure, as in “This badge will ensure your entrance to the stadium.”

The verb “insure” — spelled I-N-S-U-R-E — means to guarantee against harm or loss, as in “The company insures 500,000 customers.”

It is a common English blunder — at least in American English — to use one of these verbs as a substitute for another of these verbs.

Solution:
Memorize the definitions of the three verbs.