WHATS APP DOWNLOAD ON NOKIA LUMIA 430 DUAL SIM

We have downloaded Whats app on our Nokia Lumia 430 dual sim fone but it does not load or open when we click on the icon. Made endless calls to Cell C technical department and after deleting and re-installing they eventually advised to contacted Whats App as it is their problem. Contacted Whats app via email and all they could advise was to look up their section on FAQs. On Saturday we have been to the Cell C shop at the Galleria branch but the person who specialises in these phones was only coming in at 11:00am. My husband left his contact details to be contacted when this person arrives but never heard from him. Went into the branch again today only to be told that he comes into the Galleria branch from Thursday to Sunday. How disappointing! Can someone who has knowledge of these fones and is competent to assist in resolving this issue, please assist us. Tired of being pushed from pillar to post.