Messages not reaching Android phone after iPhone number change

my dad passed away and my mom has given my dads phone to my son. its all been switched over by Verizon. however when i text the number it still goes to my dad's iphone. my son has an android. why wont my text go to hia phone

My son is not getting my text even though he’s had his number changed to my recently deceased dad’s number

[Edited by Moderator]