My question involves employment and labor law for the state of: TEXAS/OKLAHOMA

My company currently requires that we turn in expense reports be turned in every Monday with all the charges for the previous week...myself and several other of my cohorts are oncall technical personnel in more or less constant over time...most weeks we barely have time to sleep let alone fill out an antiquated reimbursement report...Ive been told that if it is not in that week I wont be paid for it...is there some kind of precedent here...we are being reimbursed below the federal rate for mileage and per diem as well...I wouldn't have an issue with it but after 60+ hours a week of doing what we do...often that doesn't include travel...it is kind of hard to justify giving up 2 hours of the one day off I get (if I get that). Is there anything I can do here??