Verizon Galaxy S5 APN settings greyed out.

I have looked all over the forum for a reliable answer but have not found one. I have a Verizon Galaxy S5 that I am running on the Straight Talk Verizon 4G network. I would like to change the APN settings to reflect the Straight Talk settings rather than the Verizon settings but everything about the APN settings is greyed out and nothing can be changed or added. The + sign is also greyed out which does not allow me to enter a new APN. I am running Lollipop OS on the phone.
Any help on solving this problem would be greatly appreciated.