why my iphone always no service?

Start reading this support article:--> If you see No Service or Searching on your iPhone or iPad - Apple Support

After trying (to no avail) all the steps provided in that article, contact Apple Support directly (Get Support) or make an appointment (*) and have your device inspected at an Apple Store or AASP (Apple Authorized Service Provider) among this list:--> Apple – Location Selector. After checking it out, they'll give you all the available options.

Regards

Giulio

(*) You can do it:

• Online:--> Genius Bar Reservation and Apple Support Options - Apple;
• Contacting a local Apple Store or AASP among the list provided above;
• Using the "Apple Store" app, available and downloadable from AppStore.

Start here: If you see No Service or Searching on your iPhone or iPad - Apple Support and contact your carrier for help with this.

My pleasure