In my experience, many provides allow you to keep your number. Number portability is required of telecom providers in the US and I’ve successfully “ported” landline numbers to both Vonage and Packet8. I can’t speak for other providers though.
Softphones are perfect for the pandemic because using one means your employees can simply boot up their laptop or mobile device, install the softphone, strap on a headset, and they're good to go. Theoretically.

In Australian English it’s pronounced with the vowel /a:/ like in ‘part’. Problems arise when people use the /ʌ/ vowel (like in ‘up’) instead of /æ/ or /a:/. If you do this is will sound like the worst swear word in English. Many non-native speakers often pronounce the vowel /æ/ more like /ʌ/ because they don’t have a vowel like /æ/ in their first language. Many speakers of European languages will do this (Spanish speakers and Italian speakers) and also speakers of Japanese and Korean. This problem with /æ/ also means that if you say the word ‘back’ in your voicemail greeting sample, you are likely to pronounce it more like ‘buck’. remember to pronounce word endings in English. Check you aren’t dropping any endings off or mispronouncing them.
“Greetings! You’ve reached [your name and position]’s voicemail. I am away from my phone or [other important and expected job function]. Please leave me your name, telephone number, and a short message. I’ll get back to you as soon as I can, typically within [reasonable timeframe, like 12 or 24 hours].” How do I record my company voicemail?