It depends what you define as an IT department.
The "internal" IT department who deal with computers will most likely have no access to your data.
That being said, it really depends on your network and their infrastructure, however, most likely, someone somewhere will have access - but is highly unlikely to ever use it.
Your MMS has to go over your providers network and will most likely be backed up and depending on your countries regulations, could easily be logged.
This being said, unless you are a suspect, being tapped or similar, the chances of you actually being targeted or someone looking at your data, it is highly unlikely anyone will ever look at your data.
e.g. I perform hosting and web mail for many clients... I use password protection, encryption and other technologies... but, I also backup all data and if I really tried, I could decrypt/view data - but, I never would... Sometimes it just comes down to trust with your provider.