So do you or don't you have a package coming Internationally? You say the only thing you ordered is a small order. Is that past tense or are you expecting a package? Can you google search the number they called from or was it a private/blocked number? I wouldn't be overly concerned; I've never heard of a case where customs or the police tip someone off with a phone call before they bust them. Now if they call you and ask you to come to pick the pack up at the post office, I wouldn't advise you do that.
Remember postal can obtain your ip address if your using your computer or cellphone to track the package. It will give them the general area of your location, such as the State you live in, city, etc. If perhaps the package gets delivered to your address I would proceed with caution. Don't accept it by hand, let it sit outside or in the mailbox for a few days. If they're doing a CD, their warrant isn't executable until you bring the package inside your house. If you leave it sit outside for hours at some point they (LE) will take the package back or they will do a KNK (knock and talk) which you should not answer.
It's very common for customs to send seizure lists to local Drug Task Force at which time they will be assigned for follow which entails surveillance on a residence, KNK or even a possible late night garbage pick all in attempt to gather PC for a SW for your residence. The lists typical include the person the package is mailed too, address and what the package contained. Typically these are for people who order hardcore drugs like meth, cocaine, and fetty from other countries over the dark web.