Use an unlocked phone that supports eSIM. Check your exact model and region of purchase with its manufacturer. You need one eSIM for each phone.
On a compatible dual-SIM phone, keep your usual SIM and choose the travel eSIM for mobile data. WhatsApp can keep your existing registered number. Turn off automatic data switching; your home carrier may still charge for calls, texts or roaming.
These travel plans provide mobile data without a local phone number, traditional calls or SMS. You can use internet messaging and calling apps over your data connection.