not refunding credit

Have 3 contracts with cell c business and have cancelled them after they expired. Received statements showing credit owing to me on all 3. Have been emailing for 2 weeks requesting the credit and just receive the standard reply that they will contact in 24 hours! The business side is also impossible to call just puts you through to the general call centre that cant help! They had no problem taking money out of the bank accounts but seem to struggle to put back!!