Levels are unlocked based on how much you spend/how many points are collected for the month.
The next level will be unlocked immediately when you hit the minimum spending/total points collected requirement without waiting for the next month.
If your total monthly spending/points collection does not meet the minimum requirement for the particular level, you will be downgraded by 1 level in the following month.
Jan: I earned 20 points and I reach level 2.
Feb: I earned 0 points and will be downgraded back to level 1 in March.
Mar: I earned 100 points will immediately unlock up to level 5.
Apr: I earned 0 points and will be downgraded to level 4.
To maintain your current level, you will need to spend/collect enough points per the requirements of your current level.
There are many levels within the Mesra Card programme with different bonus points payout within each level for every transaction.
The more you spend, the more you will level up, the more bonus points you will get.