SIM900A and WeMoS D1 R32 (ESP32)

Hello guys, newbie here trying to do a project.
This is my first time dealing with programming and arduino related project.

I have a SIM900A GSM module and WeMoS D1 R32. I tried to connect them together and run code according to this guide:

*I have made some changes in the code which is the pin number [9 & 10] to [14 & 27] , where 14 & 27 is the digital pins on WeMoS D1 R32.

I have successfully uploaded the code.
I tried to call the number in the GSM using my phone, the serial monitor starts to appear " ? ? ? " symbol, i tried entering “i” in serial monitor to receive the call, nothing happened. (as shown in photo 1 below)

I tried using other function such as sending message or receive message, non of them works. The only thing is the serial monitor printed whatever the code wants it to print. That’s all.

I have attached my code as well. I have removed the phone number for privacy purpose, sorry for that.

I have also attached my connection below.

I have doubt after hitting around articles and guides online, can I just use any digital pins for connection or I must use the pin TX and RX on my board?

Thank you in advance.

GSM code.txt (2.4 KB)