Missing Phone Invoice from Vodafone

I purchased an additional phone from Vodafone to be added to my bill on July 13, 2023. Despite numerous calls to customer service and explanations, the phone's invoice has yet to be found. This is a very frustrating situation. How would I prove the phone's legitimacy if I tried to sell it without the proper documentation? Vodafone must address this issue as soon as possible. We're paying a lot of money, 15,000, and the lack of responsiveness and accountability is disappointing. Accurate documentation is essential not only for personal use but also for potential resale or other legal considerations. Their customer service suffers as a result of the delay and lack of response. I hope this problem is resolved soon because it is affecting my customer experience.