Where it lives
Wherever your customers already write to you.
This is the first thing to settle, and it is a question about your customers, not about technology. The bot itself is the same in every channel, so the channel is picked by where the orders actually arrive today.
WhatsApp
Your own number
The default across Italy, Spain, Portugal, the Netherlands and Poland. Meta requires business verification on your company as the legal entity, which is one and a half to three weeks of waiting. In return your customers keep writing to the number they already have saved.
Viber
Where Viber is the one people keep open
In Slovenia, Croatia, Serbia, Greece and Bulgaria this is the messenger that is actually on the phone, and WhatsApp is not. Viber has its own bot accounts, so the company keeps its own identity there too.
Telegram
Up the same day
Nothing to verify and nothing to wait for. Not the default in most of the EU, but where your customers are already on it, this is the fastest way to put the whole thing in front of them and watch how they use it.
E-mail
Nothing changes for the customer at all
If the orders arrive as e-mails today, they can keep arriving as e-mails. The bot reads the incoming mail, including an attached list or a recorded note, and writes the order up. Your customer never learns that anything changed.
A link or a QR code
Nothing to install on either side
A link in your signature or a QR code printed on the delivery note. It opens in the phone browser, records the voice note there, and needs no account, no app and no approval from anybody. This is also the quickest way to try the whole idea on real orders.
The telephone
Still the biggest channel in this trade
Most orders in wholesale are still spoken into a phone. A recorded call or a voicemail can go through exactly the same path and come out as a written order. This one is a bigger build than the rest, so it belongs in a second step rather than the first.