Check your text styles. If they have a blue Icon to the left it means they are associative and can change size depending on the annotation scale set at the lower right side of your window. Scale is very important in creating good drawings. Everything you do in model space should be created in the actual size. Civil Engineers use 1 unit of AutoCAD Civil 3D length to equal 1 foot. Architects like to use 1 unit of AutoCAD to equal 1 inch. Then if you are working outside the US you might use the Metric System.
So you have a model created in Model Space, and you want to print it out on a piece of paper. How big the paper is limits your scale. If you have 1000 feet by 1000 feet and you want to plot it on a letter sized piece of paper you have to use a scale that allows you to do that. 5 inches = 1000 feet, so you have a scale of 1 inch = 200 feet.
Now using the same model you might want to plot on a 24x36 inch piece of paper so you wouldn't use the same scale. AutoCAD Civil 3D allows you to use the same text but at different annotation scale so you don't have to write the text all over again at a different size. The text that allows the automatic changing of text size is called associative, as opposed to non associative. The icon looks like a three bladed airplane prop or a Mercedes Benz badge without the ring around it.
After you determine a text style that is not annotative, make note of it's name.
Then go to the Toolspace>Settings>Point>Label Styles>
See which style of point label you are using by the triangle icon Right click on the name and click edit
go to the General Tab, under Label, set the Text Style to a non associative type of text that you made note of above. That should fix your problem.
But don't worry, there's plenty more problems ahead, welcome to AutoCAD Civil 3D