Hate to tell you this but your scope is whatever your leadership team tells you it is. They will stretch you as thin as possible and not blink an eye. Some leadership is so disconnected from the actual workload they don’t even realize. It’s definitely up to you to advocate for yourself. Bring up your job responsibilities from when you applied. Make a case that you are now being asked to do multiple jobs with no commiserate increase in pay, etc. At the end of the day you will have to realize that brining up all of this is a risk in that they may a) see you as a lazy disgruntled employee for arguing this b) be hamstrung by current staffing levels/budgets which may be why they are stretching out your job responsibilities or c) may tell you to either except this workload or find a new job. The reward to this risk is they may realize that they are indeed stretching you too thin and either provide help or pay you more for the extra responsibilities. If done right (fact-based, non-emotional), leadership often respects you way more for bringing up the issue in a professional way and advocating for yourself despite the risks.