Yes, you can. If you purchase VIP when you have already purchased "NO Ads", then your VIP will take over "NO Ads". Once VIP expires or you cancel it, you can use the remaining "NO Ads" membership.

For example: a user buys "NO Ads" for 30 days.

On day 5, the user upgrades to VIP for 30 days.

The remaining "NO Ads" status is extended by the duration of the VIP, meaning the user has 25 days of "NO Ads" if/when the VIP expires.