CUSD Code Return

I can get answer for CUSD service with revision EC25EFAR06A04M4G but I cannot get answer from this service with revision EC25EFAR02A09M4G. How can I get answer from this modules?

Dear SmartEq_Bilisim,
Thanks for your inquiry in Quectel forum.
Please note that EC25EFAR06A04M4G is newer than EC25EFAR02A09M4G, so it is normal the old version have such issue while new one can support it. Please use the latest firmware to go on your test. Thanks!

It is unacceptable answer. Because you sell this module, so it has to work. It is working on the field. This is your mistake to send it with wrong firmware. Those are devices for just test? So you are saying do not sell our product?

Every product you sell have to work perfect. Why your engineer tested this EC25EFAR02A09M4G version completely. How you can say it is normal? Is that normal?

Dear SmartEq,
Please note that AT+CUSD command is used to control of the USSD. But the firmware version EC20CEFAR02A09M4G cannot support USSD. so it cannot get answer when you use CUSD service.

The following is the release note of the EC20CEFAR02A09M4G, please check it.Thanks!
Quectel_EC25-E-FA_Firmware_Release_Notes_V0209.pdf (719.9 KB)

So we recommend you to use the latest version EC25EFAR06A04M4G which can support the function.
Please note that the The software is constantly updated and the functions are gradually improved. It is impossible for us to wait for the completion of all functions before mass production of modules.The normal practice is to meet the needs of most of the customer’s main functions will be used to mass produce modules.
Other new functions or software bugs found in the actual use will be solved by software updates.
Therefore, the solution we offer you to solve your current problem is to upgrade the module firmware.If these two modules are purchased from our regular channels, you can contact them for after-sale treatment. Thanks!