D.B.
If you think it's a problem, then it's a problem.
Can you figure out why you are on the phone so much? Are you calling them, or are they calling you? If you're calling them, why? Are you reporting in, asking advice, discussing their lives or your life? Do you need their involvement to raise your kids? Are you discussing some other aspect of your life besides your kids? Are they calling you to find out every little thing the kids are doing?
How do you feel if you don't talk to them? Do you feel insecure or lost? Do you feel guilty? Are you delaying making a decision or taking action in your own life because you're calling first to discuss it? Do you doubt your ability to care for your kids without getting advice first or bouncing your thoughts off someone else? Did your family baby you and make you feel incapable of making adult choices?
I think you need to get to the bottom of what your reasons are, and what the payoff is for talking to others. If you aren't instigating the calls, then get an answering machine and screen your calls. Limit yourself to something very reasonable like 5 minutes per day. If you are instigating the calls, then put your phone away and plan something every single day with the kids where they have your undivided attention. It can be an outing or it can be an in-home activity: beach, park, children's library, mini-golf, nature hike (everyone takes a bucket or plastic bag and brings home treasures), sprinkler play, board game, crafts, art/painting, doing puzzles or building something with blocks or legos, reading a story aloud, playing dress up or fantasy play (superheros, knights and princesses, anything), or any of a million other activities. During that time, do not interrupt the activity for any reason except a true and real emergency. Tell the family you are having quality kid time and you think you're spending too much time on the phone.
If you can't think of things to do, go to the library for a book of games or even camp or home-school activities (which aren't necessarily academic in nature) and which don't cost money. You can make paintings for the relatives, take photos of what you're doing and put them on Facebook or email them to the relatives. You can collect rocks and have the kids wash and paint them. Or trace leaves. Collect ants and put them in a clear container with dirt and watch them dig tunnels.
The library often has passes for museums and fun cultural activities - free concerts, puppet shows, you name it. Find out from the children's librarian what's around and how you can get on email lists or check websites.
Set aside a time once a week to call your birth family and share your exploits. Let the kids tell Grandma or Auntie what they've been doing instead of you doing it. Don't let them criticize you.
If you still need help figuring out why you're doing this, consider your town/city office of child/family services to get some helpful counseling or even some parenting classes to help you transition more fully into the role of parent and away from the role of child. It's not always easy so don't beat yourself up about it, but do take steps to grow more and be more confident as a mom. The rewards are great, and your kids will be better for it too!