I think if you can make a point of STUDYING (not just reading) the regulations you need to know, and then regularly checking them for updates it will help. You probably need schedule this for a time you cannot or are unlikely to be interrupted. Think about having a sign you can affix outside to your doorway indicating that you need to not be disturbed except for true emergencies. Usually this is earlier in the day, but you need to see what works best in your office.
First learn the layout of the regulations: what types of things are located where. If they are online, you need to bookmark the contents or index; if they are hardcopy, you should add tabs (even a paperclip or sticky note bookmarking the area)
Determine which areas change most & which tend to be pretty stable. How often are there changes? daily, weekly, monthly? Figure that out, and then check all the updates out on that schedule. Can you can access the updates alone, even if it is just a list of updates--that way you can be certain that you are looking at the most recent version to answer a specific need. For example if regulations A, B, D, G & H have updates, but what you need is in section C, you can ignore the updates for that inquiry, but if it's in section D, then you need to check the update first, then the original.
You also need to schedule the time you spend on your other assigned tasks, and yes, that includes the phone answering. If answering the phone is actually a part of your job, then its importance needs to have more weight than if it is not. You might want to print and display your schedule on your wall so that others see what you are doing when; it will also serve as a reminder to you. Acquire and put up one of the posters of "Failure to plan on your part does not constitute an emergency on my part." Maybe find and put up some other motivational sayings that insprire you, as well.
As you define the specific steps that you will take to do better work, make a point of meeting with and discussing them with your boss so that he/she is aware of the steps you are taking. And pay attention to any nuances they display that indicate approval or concern with any of the ideas. Be sure to ask for suggestions, and be open to them. Work longer hours: come early and stay late, and it would help to make sure that your boss sees you there--a trip to the coffee machine where you deliberately walk past their office door, a question you could have asked during regular hours, but you ask 10 minutes ater the day if over or 10 minutes before it starts, work through lunch--eating at your desk, etc.