Question: I want to apply css to google calender iframe.  
 I had tried with Jquery but it gives JavaScript security error.  
 However I also tried [this link](https://stackoverflow.com/questions/217776/how-to-apply-css-to-iframe)

Got success but many of its links goes to 404 page as it takes my domain as base URL

Answer: 
Judging by information provided. Where when you send the +CUSD request with DCS (Data Coding Scheme) of 15. And the response from the Bkash service with DCS of 72. It looks like your modem does not support the encoding specified in the DCS from Bkash.

I found is fairly similar question and solution to this [question](https://stackoverflow.com/questions/16358610/using-at-commands-of-service-in-response-encoding-and-read-chinese-or-arabic-fo). Try and ensure that +CSCS is set to something like IRA or GSM and see what happens then with your +CUSD responses.
Hi this code is something called PDU (Protocol Data Unit). To decode it is not straight forward. you need to understand the structure first.