Hello!
I have a bit of expertise in this area. Prior to becoming a realtor, I worked at one of the largest online real estate companies (it starts with a Z ;)) in the US. My job was to fly all over the country teaching loan officers and their teams how to convert the leads the purchased through us.
The best way to contact them was through text and phone. Obviously, make sure that you're adhering to TCPA guidelines and vetting each number against the National Do Not Call list prior to calling to avoid large fines.
I found two techniques to be extremely helptul:
1.) The Double Tap: This is where you call someone once. If they do not pick up the phone and it goes to voicemail, DO NOT LEAVE A VOICEMAIL! Hang the phone up, wait about 15 seconds and call back. The Double Tap method helped my clients get in touch with about 30% more of their prospects on their initial attempt. NOTE: If someone picks up and is frustrated that you called them twice back-to-back, just say you got cut off when trying to leave them a voicemail.
2.) I learned this fantastic text message that has helped many of my clients get in touch with more prospects over the years. If the Double Tap doesn't work for you, just send that person a text that says, "Hi (prospect's name)! I just tried calling you. Are you free?" This should get them to respond and you can get them talking that way.
Just a quick tip, but thought it might help!