sim800L & nodeMCU communication...HELP!

I recently got this sim800L GPRS module: sim800

And I have this nodeMCU module: nodeMCU

the nodeMCU already comes with wifi and its a great little gadget. But.. I need GPRS communication, where there is no wifi network around. So I want to connect the sim800 module to it. Problem is.. I can't get it to communicate with each other.

ON THE UNO: I can get the sim800 module to work with an arduino UNO. I must use a ttl 5-3v converter for the RX/TX signals because the UNO outputs 5v and the sim800 module wants 3.3v. I can type AT commands on the serial window and see the response from the sim800 module.

ON THE nodeMCU: But... the nudeMCU board already works with 3.3 volts so no converter should be needed.

I've tried several test programs for the UNO, and use it on the nodeMCU and I just can't seam to have it working. I tried TX0/RX0 and TX1/RX1 pins with the same results: no communication...

help anyone? thanks