What is the optimal opsos / tariff for sending many SMS from a phone (not a service)?

Question

Email Marketing

It is necessary to send mailings from an android phone and receive SMS in response . The service I plan is semysms.net or a similar or self-written gate application for android.
The question is, which mobile operator and tariff to choose?
Sending informational messages during registration, not spam, everything is white and fluffy.

Answer 1

MegaFon, "Turn on!" + "Write!" + option

Answer 2

No matter what kind of SMS will be, the operators simply block the obvious high traffic via SMS. Experience - 2 blocked SIM cards of Beeline and Megafon. Therefore, I use the service.