ECG .dat and .hea to .mat, .csv or txt file

Hello everyone,

I have a project in which the ECG is in .dat file with .hea file and data format 212.
The next thing I have to do is to convert it in Matlab so I can use the data for further analysis.

I have already found everything about it in Physionet (Toolkit, Matlab files), but the problem is
that the .dat file has 3 signals and not 2 as usual.
The Matlab files don't work in more than two signals.

Is there anyone that can help me?
Just for the record the data are not from Physionet!

Best Regards,
mitsermath