I cannot receive OTP's

I have a airmobile number e sim with Afrihost despite several HP complaints i have little feedback from them i am not receiving certain OTP's from Afrihost clientzone and others which resulted in me switching between my old cell number and new apparently Afrihost is using a MTN backbone thus my number starts with 063 is there any reason why this might happen i did a factory reset on my phone which dit not help i still have the same issue