Update TESTING_GNB_W_COTS_UE.md

doc/TESTING_GNB_W_COTS_UE.md

@@ -44,10 +44,11 @@ Our code might not work with all 5G phones yet, but we are constantly improving
 
 *  Oppo Reno 5G
 *  Samsung A90 5G
-*  Google Pixel 5G
+*  Google Pixel 5G (note1)
 *  Simcom SIMCOM8200EA 
 *  Quectel RM500Q-GL
 
+Note1: In the version we have at Eurecom, you need to set the PLMN to 50501, and you also need to change the firmware to "11.0.0 (RD1A.201105.003.B1, Nov 2020, EU carriers)" (see https://developers.google.com/android/images)
 
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