Is our fasting valid or void if the call to Fajr and Maghrib prayers is made in Mansoura before Cairo, knowing that we follow Cairo's local time for prayer and fasting?

The time for fasting begins at the appearance of true dawn and ends at sunset, based on the Almighty’s saying: ﴿And eat and drink until the white thread of dawn becomes distinct to you from the black thread [of night]. Then complete the fast until the night.﴾ The fast is valid even if a Muslim eats or drinks before the true dawn becomes distinct or waits after sunset, but by doing so, he misses the Sunnah of delaying the pre-dawn meal (suhoor) and hastening the breaking of the fast (iftar). However, eating or drinking after dawn becomes distinct or before being certain of sunset invalidates the fast. If the muezzin is trustworthy and calls the adhan with sunset or dawn, then you must abstain or break your fast according to his adhan.