CRM Ios Android APP and Web Admin

We are a company where we make letters and applications of a limited variations. Until now we have been using viber pc and mobile app for interaction with customer but we deal so many customers in daily basis that we have no proper way of mainintaing their data and possible followup for new services so we need a system that works like a viber chat but with added business features. For customer front end [login to view URL] need an app so that customers can discuss with us on our app about which service they want [login to view URL] will always see a add button to add task or we will manually send them in conversation link or trigger the add task button to select a task so that we can label the customer. [login to view URL] we send them a Payment link or something with a price form where they can pay online or send us a photo of payment transfer slip which we will manually verify. [login to view URL] we will send them documents in a pdf or image format which will stay in our web and then they can download that as per their need until we manually remove it. For Staffs Both App + Web system is needed 1. Staffs can filter the chat list from Labeled or Recent 1. They can see all the notifications and until a label is assigned to the customer , everyone will be responsible to reply them. 2. After labeling the customer, staffs who are assigned with the Label will see their notifications. 3. They will update the work status and confirm the payment also. I have tried to put up a little thought and made a xd file which we can discuss and make changes. We dont have that much experience about app developement so you can obviously have your opinion and smoothen the workflow as you suit.