I tried to read MCC/MNC using “adl_plmnGetMccMncCode” function. It returns results which have nothing to do with reality. Fortunately, “at+cops?” returns the correct value (it returns it as one value, but for me this is acceptable).
Post the minimum compilable example which illustrates the problem you are seeing.
Sorry, I am an idiot. 
For some reason it seemed to me that this function reads MCC/MNC from SIM card. I reread documentation and understood that the values are read from some string in GSM format.
Oops!