There are so many confusions about some requirements of pensioner visas, and some facilitators can take advantage of this situation.
As you know if you qualify for a pensioner visa, you must be receiving the monthly benefit. If your pension letter states you will receive your monthly benefit starting on a future date, unfortunately the Ministry consider you do not qualify for the pensioner visa yet.
Some facilitators do not mention it due they just want to receive the money as soon as possible, but it is frustrating for expats. Especially because the other documents such as criminal background checks can expire due they are valid just for six months.
So my recommendation is to start your visa process after receiving at least the first deposit of your pension and then getting all the necessary paperwork, so you will avoid waste of money and frustration.