Amazon and minimum advertised price (MAP) is an interesting topic. Their main goal is to offer competitive pricing and they like to be in control. MAP constrains them, so it’s very unlikely that they’ll agree to it.
Even if you have an informal agreement with them, it doesn’t mean they will adhere to MAP pricing. For example, if Walmart start selling that product for $5 below MAP, then Amazon won’t think twice about matching it.
The one exception to this rule might be for larger or more influential brands that Amazon wants to keep on their side. But even then, Amazon will still want to be competitive on price.
Getting Amazon to follow MAP pricing is very difficult, but as a vendor there are two things that give you a better chance:
Having tight control over your distribution to make sure that nobody else is selling under MAP.
Managing your overstocks! Make sure that Amazon doesn’t have too much inventory. If they do, and it doesn’t sell, they’ll lower the price below MAP to try and clear it.