If the device handset unable to detect any Mmc card being inserted in it, you may first check the memory card slot for possible damaged. Clean it if necessary.
If the slot seems okay, refer to the solution below, and check some components and connection line paths.
Samsung S7500 MMC Memory Card Not Detected Solution
Samsung S7500 Mmc Connecter Pin Ways
Samsung Gt-S7500 Memory Card Not Working Problem Jumper Solution
Insert Memory Card, Memory Card Error, Memory Card Not Formatted
You may first check and trace the memory card supply voltage and ground pins connection, Then the memory detect switch, you can read voltage on this spots when the microSD card is not inserted. The memory card detection switch is connected directly to the CPU chip.