Outbound SMS based marketing crms?

Hi guys – have a bit of a unique case and looking to get some advice on our startup's situation. We're working in a developing country and in the adult industry.

Outbound marketing with SMS/Whatsapp

We're trying to do outbound marketing with SMS or whatsapp – we have a list of phone numbers we're targeting – somewhere in the 10k range of phone numbers. These are very tiny SMB customers

We want to mass message them, and if they don't answer, prod them to sign up through mass follow ups, based on templates.

If they do answer, they will respond manually through SMS or chat, and we want our customer service reps to answer them manually through a chat function – and integrate a CRM here.

We want to be able to keep slight tabs on them – drip them a message every once in a while if they don't respond and want to sign up.

Customer Success

We also want to use this function for Customer success as well. We want to use it as a channel to disseminate product updates and push our customers to take on more of our products.

What would be the best way to accomplish this?

We were thinking a mixture of AmoCRM and Messagebird, but we don't know if we can actually do outbound marketing on Whatsapp.

If we do our outbound on SMS, we also don't know how we can do any sort of response to them – we can't have a sms conversation overall.

How do you think we should handle this? What kind of stack do you think we should use?