SIM900A - AT Commands to send data to server using HTTP GET


My goal is to send GPS coordinates from Arduino to remote server using SIM900A.

I bought SIM900A from Amazon Sim900A for which I am referring SIM900A Docs

This docs simply states how to connect to remote server. From the time-gap of 3 days, it worked only once, I mean the command

AT+CIPSTART="TCP" , "mydomain.tld", "80"

gave result as OK only once but afterwards, it kept on giving ERROR as output.

How to ahead after this ? How to solve this issue ? I am totally new in Microcontroller Programming.

How to make HTTP request ? I googled for SIM900A AT commands and SIM900A AT datasheet but did not find anything.