Bad Service and Techical Issues

Ever since i took out my contract with Vodacom and ported my existing number I've had technical issues whereby certain phone numbers cannot dial my number. It tells them the number does not exist. I can dial their numbers but they cannot dial my number. I've logged this issue 3 times with Vodacom and they have not resolved this. Each time i log the complaint, they open a new request however it is an existing issue and unresolved matter