To customize your profile (defined on Telegram as "bot"), you need to send a message to BotFather (you can use this link: https://t.me/botfather), texting /mybots.
Once the message is sent, Telegram will show us the list of our bots:
From the chat select then the bot you connected to Callbell.
Once the bot is selected, click on Edit Bot.
By clicking on Edit Bot, you can choose to change the profile name (Edit Name), the description that will appear as soon as your customers open your Telegram profile (Edit Description), the description that will appear instead by clicking on the profile (Edit About) the profile picture (Botpic).
Once you have selected one of the options, all you have to do is write the text you want to add to the sections of your profile or, in the case of the profile picture, upload the photo you want to show to your customers.