You didn't identify the state you were in, but almost all states make it illegal to be seated in the driver's seat of a vehicle (a position to operate a motor vehicle) while intoxicated. Furthermore, if the officer pulled you over - that means that you were operating the vehicle at the time. (If you were not intoxicated - "didn't blow above the legal limit" - this doesn't necessarily mean that you cannot be charged with being under the influence, an officer's field sobriety test, or observation of your operation of the vehicle can still be used to show you were impaired).
If there was an open container of alcohol in your vehicle, this too is a violation of vehicle code sections in almost all states. (Regardless as to whether or not the driver is intoxicated or even drinking).
The officers had probable cause to approach you based on the call that they received.
You do have a right to contest all of this - just because you have been cited by an officer (or even if you were arrested) this does not equal a conviction.
Your license can be suspended pending the hearing - again, this is state specific, but is fairly common (not as universal as the other statutes I noted above, but again, fairly common).
If there was an issue regarding whether or not you "refused" to take the field sobriety test - this is an issue you are going to have to contest with the court or with the DMV depending on your state (usually this is contested in court as part of your overall DUI/DWI defense).
If you are not represented by an attorney, I highly recommend that you retain one promptly - these matters can be very complex as you need to deal with both procedures and evidence (it is possible to "beat" one of these charges, and I don't have sufficient information based on our "Q&A" here to tell you what kind of case you have - but hiring a lawyer is the best way to maintain your record and the fastest way to get your driver's license back - often an attorney can try to get a pre-trial order to restore your license pending a hearing (or at least get a restricted license so that you can continue driving to and from work)).