If you just need to block your caller ID for one call, you can add a prefix to the number when dialing it to temporarily block your caller ID. You'll need to enter this prefix whenever you call the number to continue blocking your caller ID. This method may not work if the person whom you're calling has an app or service that unmasks blocked caller IDs. If you have a GSM phone in the United States (e.g., most Androids), you'll usually use the code #31#, and other U.S. providers will usually work with the notorious *67 code. Other codes you can use include the following:   *67 — United States (except AT&T), Canada (landline), New Zealand (Vodafone phones)  #31# — United States (AT&T phones), Australia (mobile), Albania, Argentina (mobile), Bulgaria (mobile), Denmark, Canada (mobile), France, Germany (some mobile providers), Greece (mobile), India (only after network unlock), Israel (mobile), Italy (mobile), Netherlands (KPN phones), South Africa (mobile), Spain (mobile), Sweden, Switzerland (mobile)  *31# — Argentina (landline), Germany, Switzerland (landline)  1831 — Australia (landline)  3651 — France (landline)  *31* — Greece (landline), Iceland, Netherlands (most carriers), Romania, South Africa (Telkom phones)  133 — Hong Kong  *43 — Israel (landline)  *67# — Italy (landline)  184 — Japan  0197 — New Zealand (Telecom or Spark phones)  1167 — Rotary phones in North America  *9# — Nepal (NTC prepaid/postpaid phones only)  *32# — Pakistan (PTCL phones)  *23 or *23# — South Korea  067 — Spain (landline)  141 — United Kingdom, Republic of Ireland Tap the Phone app icon to do so. You may also need to tap the dialpad tab to bring up the keypad. If you're on a landline or flip-phone, just pick up the phone. Use the dialpad to enter the three- or four-character code you selected earlier. For example, if you're attempting to prevent your caller ID from appearing in the United States, you would type either *67 or #31# here. Without pressing the "Call" button, enter the entire phone number you want to call.  Since...

TL;DR in Vietnamese:
Bạn cần hiểu cách mà mã chặn hoạt động. Xác định mã chặn. Mở ứng dụng quay số của điện thoại. Nhập mã. Nhập tiếp 10 số điện thoại. Nhấn nút gọi.