Why I cannot get USSD notification but just an OK as a response from a GSM provider from a GSM modem?

Question

I am trying to build a C++ application to transfer credit from GSM network to another user.

In my country we have multiple GSM providers: Djezzy, Mobilis and Oreedo.

So downloaded and first tried PuTTY as well as HyperTerminal to test AT Commands before writing some C++ application based on those commands:

I tried Huawei E169 which is a USB GSM Modem. So on Oreedo provider we use the USSD code to get credit balance: *200# and I issue this command:

AT+CUSD=1,"*200#",15

It returns me the balance of my SIM credit as a charm. But when I try to get the equivalent balance from Mobilis for example using the USSD code: *222# to get the credit balance I just get “OK” but no balance information is there.

The interesting thing is: If I use my Samsung Galaxy J5 as a USB modem (after installing its driver), after I use the USSD Code:

AT+CUSD=1,"*222#",15

I get only OK on PuTTY or HyperTerminal but I can see the USSD balance notification is on my phone!? although I requested it from an application running on my laptop?!!!

I am stuck here. What I want to do is to be able to get the balance or any query I do as I intended.

Does this belong to the GSM provider or some settings of the ports like listening or anything else I am missing?