"I don't have a company mobile phone and I would only like to submit my office number. I tried submitting my office number but it said the mobile number was required. I entered my office number in the mobile number field but it didn't go through since it has to have a pin number sent via text message."

You cannot create an account for yourself without a mobile phone number. The reason for this is that the account creation process will require you to enter a pin number that is sent to your mobile device.

The only alternative to this situation would be to ask a Business Administrator to create an account for you and put your office number as the mobile number. 

The upside to this option is that a pin is not required when the Business Administrator creates the account for you. 

The downside to this option is that the app sends push notifications and text message alerts, so you will not be able to receive these alerts if you are using an office landline.