I gave my maid a 3G phone and battery charger, asked her to keep the phone on and make sure the phone always full of battery, this is part of her responsibility.
It is useless even you give the phone w/battery to the maid if she don't want to pick up the phone. I just saw that maid b4 and my maid asked her why she didn't pick up the phone and just let it rang. The maid said it's calling from her employer "por por" and she didn't answer it because "por por" was very trouble. So, you can see it's not work if the maid is unco-operative.
yes, I do not let my maid to use my home phone as she has mobile. If I fail to call her by home phone, I call her mobile. Then, ask her why the line is engaged. She always says my son plays the phone... I then remind her to put the phone on higher level and don't let my son play. She does not have any excuse for this....