ChatGPT Models selection for each chatbot

Because the prices of GPT-3.5 model and GPT-4 are different so you should let admin choose the ChatGPT model for each Chat Bot. So we can sell GPT3.5 for a lower price and GPT4 for a higher price. For the example: John Doe: GPT-3.5 Victoria Royal: GPT-3.5 16k Anthony Renwick: GPT-4 Beta Elizabeth Claire: GPT-4 32k P.s: Also add GPT model selection, chat prompt and welcome message for the default bot.