Hi
The rules on direct marketing are governed by the Privacy and Electronic Communications Regulations (or PECR) - not under the GDPRs, so the rules haven’t changed. However if under PECR you need consent to send marketing communications this will now be the new standard of consent under the GDPRs.
There are different rules for marketing to individuals or businesses, and are generally not as strict for marketing to businesses (although sole traders and partnerships are treated as individuals).
The ICO provides a checklist which sets out what you need to do when marketing to individuals and businesses via different forms of communication (emails, live calls etc) - we can't post a link here, but please search for the following: 'ico - media - for-organisations - documents - 1551 - direct - marketing - checklist - pdf'. This shows that for live calls you do not need consent, although you must screen against the Corporate Telephone Preference Service and allow businesses to opt out.
Note - the PECR are being replaced (possibly next year) and so the rules are likely to change, so you should keep an eye out for developments.
Please do let us know if you need clarification.
Lawpoint