He will not know automatically. Getting the new number to him is something you have to do directly, and the sooner the better so there is no gap in communication.
When you set up an InmateAid phone account, you receive a new number that your husband dials from the facility's phone system. That number does not appear anywhere he can see it on his own. You have to get it into his hands through a letter, a postcard, or if timing allows, by having him call your old number one last time before it goes inactive so you can relay it verbally during that call.
A letter is the most reliable method. InmateAid can get a letter with the new number, and a photo if you want to include one, to him within about a week. That gives him everything he needs to add the number to his approved call list at the facility and start using it.
InmateAid offers coupon codes to make that first letter even more accessible. Reach out to the support team and ask about available discounts to send a letter so you can get the new number to him quickly and affordably.
Once he has the number and it is on his approved list, the discounted rate kicks in from that point forward on every call.