Does change from unlimited plus to premium unlimited stop device credits

I purchased 3 phones last December and am getting device payment credits for 24 months. Since I have paid half of the payments, the Xfinity app shows I can do early upgrades on the phones. However, I do not want to upgrade the phones.

However, I would like to change the current unlimited plus plans on the phones to premium unlimited. Reason is we travel internationally and it is my understanding that unlimited plus requires you a buy Globalpass every day, but premium unlimited includes 10GB per billing cycle. 

Can someone please (1) confirm that upgrading the plans from unlimited plus to premium unlimited will NOT stop my device credits and (2) if it will not stop device credits, help me make the change.