Ensure you have the correct version by matching these specs: : Android 9.0 Pie. Memory : 1 GB RAM / 16 GB Internal Storage. Display : 6.0-inch LCD IPS. Battery : 3000 mAh Li-Ion.
If the device uses a Spreadtrum chipset (common for this range), use . If it uses MediaTek, use SP Flash Tool . premio s87 firmware link