Can I get a IUI on the weekend

So my levels have been rising and falling like the sun and moon lol.. so it’s cd 15 i called my doctor just morning and told them i still didn’t get a surge so they sent me for lab work.. so just for kicks i tested again tonight and finally received a surge according to this.. its the weekend which means they are appt only from 730-930.. should i just call from the parking lot & show up and try n do an ultrasound in the morning.. they gotta call me anyways regarding my lab work so honestly I’m just lost.. they were planning on giving me a trigger shot anyway next week so what should i do