Immunotherapy Scheduling

I am totally new to Keytruda infusions, having only had one a week ago. I was under the impression I'd be routinely scheduled for these infusions every three weeks - on the same day of the week - but to date I've not gotten any information about my next one which ought to be in two weeks on a Wednesday. I've called scheduling twice but have not yet received notification. Is it common to not get notification of the date/time until a few days beforehand?