How often is she calling during this time? Is it twice a week or so, or every night? If it is frequent, you can ask your boyfriend if he can rearrange the calling time schedule because it is interrupting your lives together. Are there times you can spend together that you know she will not generally be interrupting? You can also look into this kind of change for yourselves. If you don't think there is any cheating going on, him having private calls with baby mama might be better because it keeps your involvement with her situation at a minimum.