What you can do before you call.
If your dial is electronic, then make sure you have an alkaline battery installed. Even if you've recently changed the battery. The power provided by an inferior battery will not provide or sustain enough charge to power your keypad and work the solenoid inside your safe.
Drilled electronic lock
Electronic safe locks will shut down after a set number of attempts. If this happens then wait. Fifteen minutes is usual. The lock should stop beeping and return to normal. Then, double check your combination and work the combination without any long pauses between numbers.
If you have a mechanical safe dial then try working the combination slower and set each number exactly on the change mark.
Check that you're starting in the correct direction and the numbers and sequence are correct. Most, not all, mechanical safe dials start counterclockwise. The sequence is 4-3-2. You pass the first number four times stopping on the fourth. change direction and pass your second number twice stopping on the third. Change direction and pass your third number once stopping on the second. Then change direction and turn the dial until it picks up the bolt inside the safe and it opens.
That doesn't work then try adding or subtracting one number from each number of your combination. For example....if 74 try 73 or 75.
What to expect
The photo above left is a standard mechanical wheel pack drilled open. the piece of the lock that keeps the hook from dropping into the brass slot has been removed allowing the hook to drop into the brass circle and pull the lock block away from the safe bolts. The photo above right is the same lock from the door side. The brass rod in the top center goes through to the dial and the hole on the left in the drilled hole. Below is the same safe from the outside. The hole was filled with hardened steel and a new dial installed.
One hole in is always the goal and most of the time that's all it takes. However, two or three isn't unusually. Not in in three... then the relocker may be the problem.
The photos above are examples of relocking pins. The plates on the back of the lock keep the pins from going into the bar unless the lock is disturbed. Force off the plate and the pin spring shoots the relocker into the bar locking the bar in place.
Dial Ring Installed
On the safe above the owner knew the relocker had been engaged. So, I had to drill for the relocker. Fortunately, the relocker was behind the dial ring. After drilling twice I was able to lift the relocker, plug the holes with hardened steel and replace the dial without any repair outside the ring.