Callax Telecom GmbH | - | 0800-6601077 |
| CC-Bank | - | 0800-9988773 |
| Citibank | - | 0800-27437485 |
| Colgate-Palmolive | - | 0800-7256654 |
| Comdirect | Interessenten Hotline | 0800-2663473 |
| Condor Gerüstbau Hermann Brück GmbH | - | 0800-4378378 |
| Consors | Infoline | 0800-2525200 |
| Consors | Infoline | 0800-2525323 |
| CuraVendi | Bonusapotheke | 0800-0644272 |
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