With Cream

Anyone who knows me well, knows that I love coffee. I will take it in any form, but I have really developed a taste for good, strong coffee with a slosh of cream. This means that I often will stop at Starbucks, Dunn Bros., or Caribou in the morning. Nothing makes for a better morning than a cup of steaming coffee in the hand. Lately I have had a bit of a problem getting my ultimate order across at the drive-thru. I don't know if it is my enunciation, the speaker, or the background noise, but I can't seem to get the cream included in my order. The other day the barista thought that I said I wanted a venti half-caf with green tea. (I had said "Venti half-caf with cream, please.") Luckily she questioned such an odd order and we got it all straightened out. On the next trip through I got whipped cream on top instead of regular cream mixed in. Now, I like my whipped cream just as much as the next gal, but not on top of a regular coffee. In order to get it correct today, I went into the Starbucks. That way I could just say, "Please leave room for cream," directly without interference from anyone or anything.
Any suggestions for getting the point across without having to go in?