Security deposit required by wireless company

I'm shocked to learn that AT&T Wireless required me to have security deposit on the fourth and fifth lines. Ten years ago I was with AT&T before switched to Verizon Wireless. I liked Verizon Wireless network and its customer service. However, Verizon is a most expensive. Thus, I move all five lines from Family Sharing account to AT&T Wireless. I never pay late any payment. I have very good credit that the bank love to lend me a lot of money. I could not understand why AT&T Wireless require customer put deposit? Five high-end smartphones less than $3000 is nothing to my mortgage, my car loans.

If a customer pay late, you cut off the phone. Same thing as the other utility companies: gas, electric, garbage disposal.

Require a good credit customer make a security deposit for the fourth and fifth lines in family sharing account is not reasonable. It's suck!