Which Indonesian SIM card works best on Mount Rinjani, Telkomsel, XL, or Indosat?

Telkomsel is the sensible coverage-first choice for a Rinjani trek, with XL as the second-best option, and Indosat a distant third on this mountain. That ranking comes with an immediate caveat: no carrier is proven to work at every camp, and the mountain’s own reports contradict each other, with one account describing decent signal on the Sembalun rim and another saying rim reception disappears entirely.

The reason for the contradiction is physics rather than dishonesty. Rinjani’s trail crosses forests, ravines, and a crater basin that screens mobile towers, so a strong Telkomsel signal at the Sembalun trailhead can vanish entirely by Pos 3, reappear on an exposed ridge, and die again at the lake shore. The crater at Segara Anak is a particular dead zone, and the crater rim camps sit at roughly 2,639 meters where coverage depends on the day, the weather, and which side of the ridge you pitch your tent.

Buy and register the SIM before the mountain, in Mataram, at the airport, or in Senaru and Sembalun villages, because registration requires identification and activation can take some time. Test the card in the village while you still have a shop to return to, then decide your communication plan: message home from the village, not from the trail.

On the trek itself, keep the phone in airplane mode. A phone hunting for signal drains its battery far faster than the camera does, and the battery you save is the battery that keeps your offline map and GPS working. A power bank of 10,000 to 20,000 mAh covers a three-day trek if the phone is not burning itself searching for a network that mostly does not exist.

The honest bottom line is that a SIM card is a convenience on Rinjani, not a safety system. Signal pockets exist and are worth having when they appear, but our guides carry radios linked to the park information center precisely because no network reaches the places where problems happen. Carry Telkomsel, expect little, and you will not be disappointed at 3,000 meters.