Not necessarily. My phone number when I go back home (if anyone wants to call me) is a different number from my whatsapp number (which is my UK number, where I live). When people want my Whatsapp number, I generally give them my UK number, but I don't expect an SMS or a phone call from them because I don't even use that SIM card back home. I have another local SIM card that I use, and I also give that out as my "phone number" in case, you know, somebody wants to call.