1. If you want to remove all the hyphens then use:
Update clients set voicephone=replace(voicephone,’-‘,’’)
2. If you want to replace comma’s in the voicephone field
Update clients set voicephone=replace(voicephone,’,‘,’’)
3. If you want to replace space’s in the voicephone field
Update clients set voicephone=replace(voicephone,’ ‘,’’)
4. If you want to replace round braces in the voicephone field
Update clients set voicephone=replace(voicephone,’(‘,’’)
Update clients set voicephone=replace(voicephone,’)’,’’)