Whenever you are upgrading your smartphone then the first thing is to change the sim card for the following reasons. Cropping the sim sizes ( 1. normal sim to micro sim size, 2.micro sim to nano sim) Supported Network Generation like 3G, 4G, LTE, 5G Pricing Plans or Offers Forget all this reason in the future because e-SIM is coming. e-SIM is the future of SIM Card which will be embedded in your device itself just like the storage card. Basically sim card has the unique identity number and a small storage for your contact but if it is embedded then you can manage your sim card activation and migration with the help of your Operating system settings (iOS or Windows or Android). This concept is already launched by Apple and it is available in iPad Models but apple never said this in Apple Keynote and they named is Apple SIM Apple Said that this feature will give you more flexibility on choosing the short term mobile data plans from the variety of network provider...