Per the Obama campaign:
At approximately 11:30 AM ET this morning, the President called Governor Romney to congratulate him on securing the Republican nomination. President Obama said that he looked forward to an important and healthy debate about America’s future, and wished Governor Romney and his family well throughout the upcoming campaign.
Per the Romney campaign:
Time of call was around 8:30am west coast time. It was brief and cordial. Gov. Romney thanked the President for his congratulations and wished him and his family well.