EVERY time I replace a device on my family plan the family plan gets broken!!!

Here is the scenario that has happened to me at least 5 times....

I have a family plan with 4 phones. I decide to replace a device for whatever reason. 

I call customer service and ask them to replace the device without destroying my family plan. 

During each phone call, I spend a great deal of time verifying that the plan will stay as is and they confirm that it will remain as is.

During my next billing cycle, I get a nasty text indicating that all of the phones besides the phone I am using have been cancelled.

I am then charged full price for service for one phone!!!!

This issue has been happening for about 2 years ago and every time this happens I have to call Sprint Corporate to get it fixed. I am given credits anywhere between $10 and a free month of Service.

However, this costs me 2-3 hours of my life every time this happens along with consequential stress and loss of service for minor children when they need the phone the most.

I have been told to always contact a supervisor when I call in just to change my device so that this won't happen!!

Even with this, I have to wait for a supervisor and articulate the situation and authenticate myself to first line customer service which wastes even more time!!!

What is the problem here?