How do you have the button layout configured?
Are you using a Layout Grid to control the different presentation options across Desktop, Tablet and Mobile?
Tilt your phone landscape and you will likely see the buttons align horizontaly next to each other. Simply because now there is enough space for the buttons to fit next to the pagination arrows and pagenumber. As you can see datagrids do not fit very well on the smaller screens of the phones. My advise would be to replace the datagrid with a list view or a gallery. That will give you much more power to create a beautiful design.